Streaming league of legends with OBS issues

[Daviddenek]

Well the thing is that when I stream with OBS and I use youtube or any other stuff its okay, the problem comes when I start playing LOL in stream, fps mlows from 200 to 80-100 fps and the game gets lag amd if I stop streaming with OBS it goes the same way. But if I close OBS the game is perfect again.
btw i have ryzen 5 3600X and graphic card nvidia gtx 1660 SUPER OC