trolls and spam

There must be some kind of system.

It is very difficult to check and delete everything manually.

Here you need either some kind of team of specialists who will work for you or look for some kind of program to build this system on automation. 
Perhaps you will find the answers here gyre.pro/blog/how-to-deal-with-trolls-spam-and-negative-comments-on-your-live-streams It seems like the way this article was described was not bad.