Motor mechanic failure

I took my car polo 1.4 trendline( FSS 566 MP ) to be fix with the problem of accelerator that was not functioning only cause the engine was starting itself to Trichardt Wheel Alignment Fitment Centre(***) to the guy called Tommy who promise will fix my car, then after Tommy did some test with his machine to my car he says to me he found the problem and it is throttle/flow meter valve and he charge me R7200 to fix it which I made the deposit of R3600 but after he replace with new part the car was still doing the same problem accelerator still not functioning then he decided to take the car to VW***) in trichardt. When I got the call from VW informing me about my car things where now worse than it was before, the car engine is no longer starting, the computer box is dead or not working anymore so I don't know between Tommy and VW who damage my car but all I want is to see my car be the way it was before cause they're the one's who damage the computer box and make the engine not start again