[Tervuren]

Basic rule, don't try to negotiate new car and trade in at the same time.

Best to start with the price of what you're trying to buy.

After that, work on trade in.

If trade in doesn't go well, try to sell it to other dealers, and if you get a better deal, sell your car to dealer, buy car you negotiated.

Trying to negotiate both at once indicates you feel under pressure, and are likely to be a poor decision maker. Humans are also worse at balancing multiple thoughts, so it will be default keep someone from thinking properly.