I felt the urge to tell a friend to talk to me whenever he feels the need to self harm.
That is nice of you. What made you feel the need to ask him to talk to you?
I was the only one who witnessed his first suicide attempt, however I'm sick of his self-harm behavior.
I can understand your feelings. If your friend self-harms, it's good to be there for them when they need to talk. You might suggest to your friend to get professional help to stop him from future behaviors.
He doesn't listen to me. I just wanted him and others to stop this behavior.
It could get annoying in a situation like this where you feel they are not listening to you. But you need understand you're doing a lot by being there for them. Continue to offer your support, and also help him find some therapy to help him get back into a good mental state.