How to create form for 2 or more users?

Hi everyone. I fairly tried to solve my problem with wix tutorials, but it is impossible to find there something but obviouse things. (( So I need help.
My site is something like deal-making solution. It should have collections “Goods”, “Users” and “Places”. And I need something like common form for users can make an exchange deal. First user will chose goods from the collection and its amount, then chose the place where the exchange should have place and thus form a sort of order. Other users should have ability to look through placed orders (with filtres of couse) and “sign” chosen order. And all this information should be stored in database.
How to do this?