Car repaired without consent ?

Hello, after a driving accident I asked the workshop of my trust for an appointment to repair an accident damage according to previous estimate.. Car delivered in the workshop, then came a call, which the damage would now be roughly estimated at approx. € 8.000,00 and the employee for the creation of the KV would have preferred an expert with it … so evaluator ordered, who looked at the whole and then came a few days later the report .. the review he had stopped the car in stock exchanges and also recorded 3 offers of purchase in the report.. and also noted that from an economic point of view a repair does not constitute an obstacle… o.k. something thoughtful and then informed the highest bidder the acceptance of the purchase offer.. so far so good .. then called at the workshop and informed that the car is sold … what then came down to me… the car would have been almost finished repaired and can be picked up tomorrow… is this procedure of the workshop right ??? Can the vehicle be repaired without consent to the cost estimate ?? Is the phrase “date for repair .. already as order after previous KV? Do you have here possibly tips for me, how I should proceed now ? Thank you already in advance