How do I stop hackers from accessing my home network

Hello, I am running Bitdefender Ultimate Security and BD VPN, with the location set on automatic. I watch a lot of YouTube. I can tell when hackers are watching my monitors because the sound quality deteriorates. Or, my email address pops up, in a little window, on my monitor and doesn't go away when I change tabs. Or, I'm on a sensitive site and I get a pop up that says "Error Click Here". Any suggestions on how to block hacker's access to my network will be appreciated.