How to handle a relationship, my girl sleep with other man?
I feel depressed.We were three (3)years in relationship,one night she hang out with other man and sleep with him.

I am going to assume that by sleeping you mean had sex with him. I would throw her out, I personally don't accept the minimal form of cheating much less her going all the way with another man. But, if you are one of those guys that accept it and you are enfatuated with her, you can talk it out and try to work things out. By TALKING.

If that was me I would leave her. Three years in a relationship and she does that man. I'm sorry to say but I agree with mmresd

Walk out of the relationship. Unless you want to stay with her and tolerate more of her cheating.

Omg ditch her! Things won't get better if they are already that bad,they will get worse! She's taking advantage of you and probably your $(gifts)!

Handle your business first, cry later. Why did she cheat, did you ask? (or demand would be my position)

dump her and incinerate all photos,gifts and other things you have of her. It will be hard, but face the facts, she cheated on you her 3year love with a random guy.

either stay with her and risk her continually cheating on you cause she then knows she can, or dump her, move on and be happy! Not saying that breaking up is easy, but no use staying in a relationship where the girl doesn't have any respect for you!