It's typical for the other side to open negotiations with crummy conditions, not different from what happens millions of times a day in bazars all over the worl

It's typical for the other side to open negotiations with crummy conditions, not different from what happens millions of times a day in bazars all over the world. I would venture a guess, that the potential buyer is aware of your inexperience, and trying to pull one on you. Don't let them FUD you with comments like 'changing the tone' once legal representation gets involved. They clearly seem to have invested time and effort to vet the deal, so you very likely have a strong position. I'd take my time, as excited as you might be, don't get desperate, and try to find a good M&A lawyer to provide you with guidance. Ask for referrals from people you trust.