Question about my pc lag/disconnection

[M0nSt3R]

Hey guys, I have like a horrible FPS lag and I aint gotta clue how to fix it and I gotta minimize it to get it out of the way, but sometimes I cant get back ingame it stays at the menu screen and I keep clicking the resume game and nothing and if I press enter it freezes and I gotta log off and log back into my PC account. Its really annoying, if one of you had this problem and you fixed it please talk me through steps please?