Patient: VW Polo 1.2 2004 193kkm

I was driving when recently check engine poped up. The engine started rattling and max rpm I could achive was 1.8-2 K. Reaction on gas pedal was weak (jerking) and it was struggling to move.

1. It’s my grandpa’s car so I don’t know if the filters were changed recently.
2. Oil level was fine all the time and the car wasn’t overheating as well

What could be the problem? What can I inspect before mechanic will see my car?

Thanks in advance.