Sale of commercial vehicles to dealers. What do I need to consider?

Moin, I would like to sell our commercially used 2020 Seat Leon this month. We have a small company in the social sector. The car is used more than 50% commercially and is put into the company. We are subject to the small business regulations and can not identify VAT. We want to sell the car to a flag dealer or HUK online or we buyin…. depending on who wants to pay more. What do I have to observe contractually? How to “sell under exclusion of warranty”?