To be relatively secure:
1. Use a VPN service.
2. Use DuckDuckgo or startpage.
3. Get a secure email account such as startmail.
4. Use Linux as your OS.
5. Browse in private mode on your Browser.
Typo on #1.
How do you get over the “connected to the Internet” thing?
If you are connected, they can sniff your traffic no matter what you do. It is physically impossible to be connected and disconnected at the same tie.