It sounds like it could be a broken cam belt, but and half reasonable auto shop would diagnose that.
If it is a broken cam belt it would need new cam belts (3 of them), heads off to check valves and pistons (not an easy job) and possible some new valves and maybe a piston or two and maybe liners. Normal way of fixing a bad case of that would be to find another used engine, fit new cam belts etc. and fit that.
At the other end of the scale, it could just be a camshaft or crankshaft position sensor.
You really need to get a good mechanic that you can trust to have a look at it.