He already wrote to the other forum admin. And as OP said, Naster was kicked from the forum, and his sales thread was locked by the administrator. One more thing is, Writing to the admin not going to help him to return his 26K euro. I am still confused about his accusation because, Naster claims that OP's back locked the 26K euro. Not Naster's bank. So based on Naster's claim, he said he didn't receive the 26k. So, How can he send 26K crypto if he didn't received that 26k on his bank?
So I would like to ask OP to provide the proof that you have send him 26K to his bank and it was successfully released. If you have send him 26k and it wasn't released but locked. There's might be a problem.
Naster used a drop which simply means that for receiving money he used someone else bank account (his partner or who knows whos)
OP sent funds to this account knowingly or unknowingly that it is Naster partner account which means Naster is fully responsible for the funds. There is no way to chargeback these funds. (At least if it was in € and SEPA bank transfer)
He is claiming that funds got locked on that account which I highly doubt, but if thats the case this bank will either release funds after providing some proof or they will issue refund. They will never keep that money, it is against the law.