Re4litysibbyowlcometdo they say that if you make a mistake, or are they just being toxic in general?
General
Toxic people will be that way no matter what. So don't get too irritated by them. I know it's easier said than done but a simple local mute in mumble goes a LONG way.
Always pushing yourself to perform at your best, playing smart, and learning from the mistakes that you make will help you so much in the long run. Even if you're kind of at a "plateau" point where you're trying and not exactly getting better, seeking advice from someone that knows the ins and outs extremely well (you could ask any higher level player at the end of a pugchamp game for example) and that can help you to diagnose what you're not doing very well and work on it.