@Sofy

Yes, I already did Step1, and Step2 but no luck, no good results.

This is why I decided to write a topic, and contact someone who can give me more clues.

Update of my story.

I had received some info, that my hostings MySQL is  [mariadb 10.3.22]

And I should try to look around in wpforo files if there is something like:
ENGINE=InnoDB and try to exchange it into ENGINE=MyISAM

Now I do not know mych about this stuff, and I will not waste my time doing some crazy experiments to see if it will work or not.

Any ideas how to fix it?

... or just simply start to look for a new hosting?