You'll need to be more specific: are you using GitHub to host your website (via GitHub Pages) or just store your code in a repo (private or public)?
In either case, GitHub can be perfectly safe... but there are definitely things to consider re: security, privacy, etc. Happy to chat if you need to pick a brain.
Kind of yes and no.
There are private repositories where only you decide who have access to.
On the other hand, github uses all the code from all the repositories to train their AI - Copilot.
If you're concerned about privacy, try gitlab, bitbucket or other git repository services, or try svn, or use git locally