Hi,
"make a deal" reach an agreement. Often, but not exclusively, used in buying/selling.
Me: I'll give you $20 for your watch. You: OK This means we made a deal.
Me: I'll wash the dishes if you'll dry them. You: OK This means we made a deal.
"reach a deal" It's similar, but 'reach' suggests that our negotiations took more time.
Best wishes, Clive