Workshop is not finished with repair – insurance doesn’t want to take over car rental…

Dear community, after an accident I have now since 1st August a rental car for the duration of the repair of my BMW 3. So far so good. I have now received the rental car from the insurance until 14. August. Unfortunately today the workshop informs me that I can pick up my car only on Saturday. All right, I think and call again at the insurance to release the rental car from Sixt. Far missing – the insurance is the opinion that this from tomorrow now my problem is how I get into work. However, the company Sixt needs a release by the insurance company and at all they give an accident replacement car anyway only 2 weeks ago. That is “agreed” with the insurance companies. My lawyer believes that I should not let my hair grow gray. The rental car is still available to me free of charge. However, if the insurance company refuses to continue to pay the rental car, how do I get into work for the “two days”, without having to get a rental car myself and possibly stay on the cost? The report provides for a repair period of 6-7 working days, which the workshop has now already exceeded. The exact reasons are not yet known to me, but I think that this is correct and was unavoidable… Does the workshop have to take over the rental car for the rest of the days? Who do I have to turn to if I still need a rental car? Thank you very much! Greetings, Jürgen