Firewall for my devices (iPad, iPhone, surface) on a shared home WiFi network?

I am renting a room and using shared home WiFi network. The owner has setup a Netgear WiFi range extender for me. I have another roommate on the same network along with the owners. I use Nord VPN. Since a few months I have been getting weird emails…someone opens accounts (like Snapchat, SoundCloud, Pinterest etc.) in my name constantly. I close one account and two more gets opened. I accessed those accounts and they had photos and stuff, so someone had been using them. I noticed that date of birth in one account was a date of significance to me (not my dob) and year in the username was a significant year related to that date. So it is confirmed that I’m hacked. On top of that yesterday I accessed my new website hosting service and made some changes to start a website, today this person opened an account for hiring employees. I believe someone can access (Hack into) my devices through home WiFi. Is there a way to monitor who is accessing and stop it in real time like a firewall. I use iPad and surface pro. Any advice to secure my devices?