Mercedes Maemo the biggest frustration and dissapointment

If I knew I would struggle like with a Mercedes 2019 model I would have never bought my Mercedes from Maemo. I bought my car in November 2020 and my car started giving problems in April 2021. Since then up to date, my car has been giving problems. I've got mu car a year now but only drove it for 4 month. Every time I take my car back for exactly the same problem as always, there is something new that is faulty and must be replaced or rectified. In December the Owner shouted at my husband that we decided we didn't want the car and it is fixed and tested and everything is working as it should be working. Last week I found out that the issue is still not fixed. How can a workshop of a international brand operate like this, as they are able to pin point and fix the issue. Maemo received their money from the bank for my car and I am paying my monthly installments, and Maemo provided me with frustration and disappointment towards Mercedes and a faulty car that was returned to them 6 times and standing next to the road twice. I want a refund and cancellation of contract as they are not holding up to their end of the contract by providing me with faulty free car. This is written without prejudice to rights.