How do I help my friend who has severe mental health struggles?

My friend is struggling badly with his mental health and I don’t know what else I can do to help him. I have tried giving him space he’s asked for, tried to show him how much I love him and care for him, let him be vulnerable with me… the list goes on of everything I’ve tried and I’m at the point where I don’t know how else I can help him.

Any thoughts are appreciated!