Triple donk vs Overpair

I expect you don’t have any info on the player. I would fold the river.
It’s not to likely he would 3barrel bluff against you on a coordinated board like this.

Cheers,
SDK1987

I agree with SDK.
Donks are more often weak than strong but there will be some strong hands also, and draws. Now the flush has completed and villain 3barrels increasing his sizing OTR. It looks strong and I doubt this would be a bluff very often. You are right that you wouldn't then have many hands that could call with and you can be exploited because you fold too much. But this is still exploitative folding where you are exploiting villains tendency to donk 3barrel with too value heavy range.

Very often you will see Ax hand, turn to bluff OTR. AQ also is possible.

OTF: Could I raise ? I dont want to isolate into sets and I dont know what should I do if he will reraise me, or can I go r/f probably r/c?

This is the most profitable line, but you must fold vs raise.