I'm not going to talk to a depressed friend
Why would you not communicate anymore with them?
I decided this way in my head
You should try to help a friend who is depressed. It is best to get him into therapy.
What if he kills himself. That will be really bad for him to do since I'm alive.
Right, so I suggest you don't stop talking to him and make sure that his life is worth living so that he will feel less depressed. If you can, try to maybe invite him to go out sometimes.