Hi Cirieno --- I agree it's not very nice to see a car you've agreed to buy still being advertised at all.... and even worse to see the price has been lowered, which is why you must try to get their agreement to lower the price out of goodwill.
Had they sold that car onto anyone other than yourself, then they would be in breach of their contract with you ... accordingly this would leave them open to legal action brought by yourself for them breaching a legal contract, which could include compensation and the return of deposits already paid by you.