hi problem here

Ok so I got this friend that I've known since wayy back like 9 years he had this girl and since the beginning I knew it wasn't a good relationship, jelousy, disrespect, and a lot of lying, besides all that they managed to last 3 years which I never saw him all this year because she made him stay home and not talk to no one, he did the same to her, but she didn't really listen.

Anyways make a long story short they broke up like 3 month ago and now he just devestated he tells me that she lied to him, that she was too jelous and that she says that she cheated on him, of course that's what hurts him the most. But then she would say is a lie, but when they got mad she would say it was true(crazy)....

Ok so my question here is how do I get my friend to forget about her he is devastated, he can't sleep, he cuts himself, and once he try to get in front of a moving train. Im really worried about him he was never like this for any girl, I want to help him I don't want him to hurt himself.

how to help him forget her
what do I say to him to make him happy
what can I do to at least help him get her back

Pleae help

You can't fix this self-destructive guy. That girlfriend was a symptom, not the cause. The root of the problem is HIM, and there is not a single ting you can do to change him, he has to do that for himself.