Customer wants to Buy full rights of my logo. Confused about the process

Hello, a customer wants to buy full rights to my logo and after that, I will delete that logo from my portfolio.
I’m confused about the process, how should I proceed and should I have to pay a percentage to envato?

They cannot do that through envato

It would need to be a private arrangement BUT you/they cannot stop people who have already licensed the item from continuing to use it.

Got it.
Very thanks for the quick response!