p0343 camshaft position sensor fault

I bought a used c3, great car and all but it had the engine light on. After plugging in an OBD2 scanner in I got an error p0343 which indicates fault of camshaft sensor A. The engine ran a little rough and instead of getting 6l/100km I was getting 9-10l/100km. I bought a new camshaft sensor from autodoc and asked a friend that is a mechanic to change it.
This is where problem starts. After a change engine started really rough the rpm needle was bouncing up and down until it stalled 30s later. Than we played around a bit till we put back both camshaft sensors that were originally in just reverse and the car still gave out codes for both sensors but it ran nicely, the only thing was ESP was not working and I couldn't turn it on. After that we tried unplugging the battery and that helped the ESP problem but rough running and stalling of engine came back. We than gave up and tried moving the car an we noticed that car has no power steering.
This is the situation where we at the only thing it that on the screen it says antipoluttion fault when I turn on the car but that's from before but it disappears a few times when playing with the sensors.
Could it be an internal computer?
Any help helps. Thanx.

Unfixable wrote: ↑Tue Jun 25, 2019 11:14 am it disappears a few times when playing with the sensors.

You would probably be better off connecting Lexia (from here) and go through all the configuration and fault finding.

But don't forget the classics for cam sensor, and check the cam timing

Power steering, check the alternator voltage and see the faults on lexia.

Maybe you just bought someone else's problems.....