when i run “sudo apt-get install” in terminal these are the errors

When I run sudo apt install in the terminal, I get the following error messages:

Traceback (most recent call last):                                                File "/usr/lib/cnf-update-db", line 8, in <module>     from CommandNotFound.db.creator import DbCreator   File "/usr/lib/python3/dist-packages/CommandNotFound/db/creator.py", line 11, in <module>     import apt_pkg ImportError: No module named 'apt_pkg' Reading package lists... Done W: GPG error: http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY BC711F9BA15703C6 E: The repository 'http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.4 Release' is not signed. 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/webupd8team/sublime-text-3/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: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi' E: Sub-process returned an error code