I'm not a gamer... but see the pinned post at top of forum about posting an OBS log so you can get help
No one can help you with what you've posted as there aren't enough details. Thee are literally hundreds of possible settings/causes for you system to have an issue, many having nothing to do with OBS
Video encoding is hard work for a computer. If your CPU/RAM/GPU are near maxed during game play, then adding streaming on top of it will be difficult and require a lot of optimization (and possibly lowering of expectations). So... it depends ;^)
