50k what? Not $US surely? Just think, long and hard before replying: why would anybody offer you $50k for a domain that's worth, probably, between $1k and $2.5k? $5k at the very most. How much do you really think it's worth?
Was this offer passed on by Afternic (I see Porkbun is registrar and DNS pointed to Afternic in whois)? This was happening on GD quite a lot recently, I received a few myself, so was looking to see if this is GD too as I thought they'd taken measures against the perpetrators to prevent it happening.
Anyway, they'll try to dictate to you how to proceed, which includes passing everything over to their "legal representatives" to be checked properly. No money will ever come your way.