Ubuntu 18.04- apt-get update error

I got this error:

chandramauli@BHASHKARACHARYA:~$   sudo apt-get update Hit:1 http://download.virtualbox.org/virtualbox/debian xenial InRelease Hit:2 http://repo.mysql.com/apt/ubuntu bionic InRelease                                                                                        Get:3 http://linux.teamviewer.com/deb stable InRelease [9,388 B]                                                                               Get:4 http://dl.winehq.org/wine-builds/ubuntu xenial InRelease [6,257 B]                                                                       Get:5 https://dl.winehq.org/wine-builds/ubuntu bionic InRelease [6,257 B]                                                                      Get:6 http://archive.canonical.com/ubuntu bionic InRelease [10.2 kB]                                                                           Hit:7 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu bionic InRelease                                                                          Hit:9 http://www.geogebra.net/linux stable InRelease                                                                                           Ign:11 http://old-releases.ubuntu.com/ubuntu bionic InRelease                                                                                  Ign:12 http://old-releases.ubuntu.com/ubuntu bionic-updates InRelease                                                                          Hit:13 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu bionic InRelease                                                                Ign:14 https://mkvtoolnix.download/ubuntu bionic InRelease                                                                                     Err:4 http://dl.winehq.org/wine-builds/ubuntu xenial InRelease                                                                                   The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F Err:5 https://dl.winehq.org/wine-builds/ubuntu bionic InRelease                                                                                  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F Hit:15 http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu bionic InRelease                                                                Ign:8 http://www.bunkus.org/ubuntu/xenial ./ InRelease                                                                                         Ign:10 http://www.bunkus.org/ubuntu/bionic ./ InRelease                                                                                        Err:16 http://www.bunkus.org/ubuntu/xenial ./ Release                                                                                         404  Not Found [IP: 144.76.6.86 443] Ign:17 http://ppa.launchpad.net/sun-java-community-team/sun-java6/ubuntu bionic InRelease                                                   Hit:18 http://ppa.launchpad.net/uget-team/ppa/ubuntu bionic InRelease                                                                          Hit:19 https://mkvtoolnix.download/ubuntu bionic Release                                         Ign:21 http://old-releases.ubuntu.com/ubuntu bionic-backports InRelease                                                     Get:22 http://old-releases.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]                      Err:20 http://www.bunkus.org/ubuntu/bionic ./ Release                                                                                     404  Not Found [IP: 144.76.6.86 443] Err:24 http://ppa.launchpad.net/sun-java-community-team/sun-java6/ubuntu bionic Release           404  Not Found [IP: 91.189.95.83 80] Err:25 http://old-releases.ubuntu.com/ubuntu bionic Release                  404  Not Found [IP: 91.189.88.153 80] Err:26 http://old-releases.ubuntu.com/ubuntu bionic-updates Release   404  Not Found [IP: 91.189.88.153 80] Err:27 http://old-releases.ubuntu.com/ubuntu bionic-backports Release   404  Not Found [IP: 91.189.88.153 80] Get:28 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 Packages [460 kB] Ign:28 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 Packages                                                               Ign:30 http://old-releases.ubuntu.com/ubuntu bionic-security/main i386 Packages Ign:31 http://old-releases.ubuntu.com/ubuntu bionic-security/main Translation-en Ign:32 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata Ign:33 http://old-releases.ubuntu.com/ubuntu bionic-security/main DEP-11 64x64 Icons Ign:34 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted i386 Packages Ign:35 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted amd64 Packages Ign:36 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted Translation-en Ign:37 http://old-releases.ubuntu.com/ubuntu bionic-security/universe i386 Packages Ign:38 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 Packages Ign:39 http://old-releases.ubuntu.com/ubuntu bionic-security/universe Translation-en Ign:40 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata Ign:41 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons Ign:42 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons Get:43 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse i386 Packages [4,148 B] Ign:44 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages Ign:45 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse Translation-en                                                         Ign:46 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata                                                  Ign:47 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 48x48 Icons                                                     Ign:48 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 64x64 Icons                                                     Ign:28 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 Packages                                                               Ign:30 http://old-releases.ubuntu.com/ubuntu bionic-security/main i386 Packages                                                                Ign:31 http://old-releases.ubuntu.com/ubuntu bionic-security/main Translation-en                                                               Ign:32 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata                                                        Ign:33 http://old-releases.ubuntu.com/ubuntu bionic-security/main DEP-11 64x64 Icons                                                           Ign:34 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted i386 Packages                                                          Ign:35 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted amd64 Packages                                                         Ign:36 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted Translation-en                                                         Ign:37 http://old-releases.ubuntu.com/ubuntu bionic-security/universe i386 Packages                                                            Ign:38 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 Packages                                                           Ign:39 http://old-releases.ubuntu.com/ubuntu bionic-security/universe Translation-en                                                           Ign:40 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata                                                    Ign:41 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons                                                       Ign:42 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons                                                       Ign:44 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages                                                         Ign:45 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse Translation-en                                                         Ign:46 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata                                                  Ign:47 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 48x48 Icons                                                     Ign:48 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 64x64 Icons                                                     Ign:28 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 Packages                                                               Ign:30 http://old-releases.ubuntu.com/ubuntu bionic-security/main i386 Packages                                                                Ign:31 http://old-releases.ubuntu.com/ubuntu bionic-security/main Translation-en                                                               Ign:32 http://old-releases.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata                                                        Err:33 http://old-releases.ubuntu.com/ubuntu bionic-security/main DEP-11 64x64 Icons   404  Not Found [IP: 91.189.88.153 80] Ign:34 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted i386 Packages Ign:35 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted amd64 Packages Ign:36 http://old-releases.ubuntu.com/ubuntu bionic-security/restricted Translation-en Ign:37 http://old-releases.ubuntu.com/ubuntu bionic-security/universe i386 Packages Ign:38 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 Packages Ign:39 http://old-releases.ubuntu.com/ubuntu bionic-security/universe Translation-en Ign:40 http://old-releases.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata Ign:41 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons Ign:42 http://old-releases.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons Ign:44 http://old-releases.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages Reading package lists... Done W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.winehq.org/wine-builds/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://dl.winehq.org/wine-builds/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F E: The repository 'http://www.bunkus.org/ubuntu/xenial ./ Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://www.bunkus.org/ubuntu/bionic ./ Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/sun-java-community-team/sun-java6/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://old-releases.ubuntu.com/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://old-releases.ubuntu.com/ubuntu bionic-updates Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://old-releases.ubuntu.com/ubuntu bionic-backports Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/sources.list:53 and /etc/apt/sources.list:54 W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/sources.list:53 and /etc/apt/sources.list:55 

Kindly help me to from these issues. Any help will be appreciated.