Ah, thanks, now the screenshots make more sense to me.
It looks like you lost in all 4 forums in the last 1 year ~50% of your activity.
The international one is nose-diving from the start but the other 3 were growing until 2017-2018 and since then they are declining.
The trend for all 4 doesn't look good. Something must have happened in the last 18 months. If you can figure that out, maybe there is sth. you can do to stop it. If you don't know what it is and there is nothing common between all of them, it probably is the effects of Google deranking you. What does the search console tell you about your rankings? How were they 2 years ago and now?