Bad workmanship

My car went to Bosch in the beginning on the year to have a problem sorted out I did not know what the issue was but they told me they will strip and quote they found the problem and it was with my boost pipes. Two weeks later i fetched my car and the engine light stayed on. I took it back to Bosch and the mechanic told me it was fine I just needed to drive out the air.The engine light would come on and go off once every month. Recently I got tired of the problem and had the car dignosed at another mechanic when we looked at the engine we found wires which had been cut by Bosch to diagnose they did not cover the wires the cut . Also loose nuts were found in the sump tray and my air displacement sensor was also not grounding. The part they 'fixed' was loose and not held by bolts. My alarm cables were cut and joined again and the support arm that holds it in place was broken. They assured me the work done on the engine has a 6 month warranty. On the 30th of March I planned to go to Bosch and leave the car to be sorted out but the country went on lockdown. My car is standing in my garage and it needs to be fixed . Please contact me on a way forward.