My customer report me and reimburse his payment, but I already provide my service

[Demon1CeAce]

Hello, I'm a freelance artist, about 2 weeks ago, one of my customer did reimbursed almost all of his commissions payment by reporting me and I lost my money, I didn't realize that until few day later I found that my account balance went negative, after checking some stuff I figured out what happened.

He reimbursed his payment, almost all of them, and report me. I contact him and ask what's going on, he did respond, he said he didn't know that would happen to me (losing money), he apologize and promise to give me my money back, I did give him a chance because he was my friend and I trust him, but it's been a while and he's not responding so I decide to make a move and post this here (sorry if I post it in wrong category)

What should I do and what can I do in this case? I have a proof that I did deliver my service (image files, date) also recently I receive a notification about reported case (reported by that guy) as showed in the image below

I did respond to it and show my proof and I did gain my money back, but only for one of his payment. Do I have to wait until Paypal team finish checking every reported case and show them a proof that I did my service?

Thanks!