AU did not exist: charging pressure limitation valve except target range

My V 70 D5 Premium didn’t pass the AU for the first time today with 176tsd. Something with the turbocharger, my unfriendly opinion. Error message is PO 244 charging pressure limitation magnetic valve out of order. The turbo is gone, the valve, if that were it, would come 800 teuros, the complete Turbo 1000 without installation. I don’t trust the roasting, the car runs like cut, 1200 km with a tank in mixed operation, from time to time, once a month comes the message: engine maintenance required after locking at 2500 touring. Shut down and start again was the solution until now. As a woman I don’t trust a mechanic, they always hold you for stupid and clapping in the most expensive rep. Does anyone here know the message and has an idea for the solution? Thank you and nice greetings!