Buying a Business and all its (highly sensitive) Data - How to navigate GDPR?

Does anyone have experience in negotiating the purchase of sensitive customer data w.r.t. GDPR? The business operates in Germany, and has physical retail and ecommerce. I am currently looking at a deal that includes the transfer of the website and email accounts to me. Of course, I would like access to the full history of the email accounts, including all past communications with clients and suppliers. The seller wants to sell me a blank email accounts, because he has GDPR-concerns —> selling people’s personal data (in this case names, addresses and data from which sexual preferences can be inferred) without their explicit consent is against GDPR. To me, the customer data is not as important as the communication with suppliers (which includes all history on pricing, incoterms, and negotiations). Separating the data would be a Herculean task.