The built-in system is quite good.
You can set the advert to 'Pending' to let people know and stops them making offers but you can turn it back again if it falls through.
When I want to sell something I'll start with the highest price I think is reasonable given the rarity, scarcity, condition, performance etc to see if someone is keen enough to buy at that price. If it doesn't sell I'll lower the price after some time depending how fast I need to shift it.
If it still doesn't sell at the lower price then I'll keep it 😁