Disconnects over and over again.

My game starts perfectly. Making SBC and Evos are all doing well. Only when I actually want to play a game does he always get stuck just before the game starts or when I am just in a game and he disconnects. Also sometimes when I try to play a game the screen turns black and then  I can still here the commentary, but the screen stays on black and I can't do anything and I need to close the game. On different games or apps everything works perfectly fine and my internet is better than ever. How is it possible? What do I need to change? I deleted the game and downloaded it again. I did a hard reset on the router, but nothing changed. This problem is since last week.