My girlfriend is cheating on me..

So I've been in a relationship with this girl for 7 years and all of a sudden a few days ago I found pictures of her with another guy.. So I asked her what she was doing taking pictures with another guy and she said to me that he's just a friend, but I then realized she was lying and they always flirt with each other in front of other people and she never mentions me. So I asked my friend he's a bit on the short side and always wears blue and he showed me that she is cheating on me.. Her name is xayah and I think she is cheating on me with some dude named rakan.. Idk what to do.. I know this isn't the place to talk about stuff like this but I need your help guys. :( Thanks League Community.