It does sound like a job for an engineer, but you could just see if you have lowered the feed dogs by mistake, and that is why the fabric is not being gripped.
It will only need oiling if you have metal gears etc - if they are plastic the oil will spoil it. I would see if you can find a sewing machine shop or engineer who can help you.
Sounds like it needs a service. You could try cleaning it thoroughly with compressed air/ little brush including the bobbin holder, you may find threads tangled up inside, and then oiling it, but if no joy take it to a professional.
I have an old but very serviceable Pfaff sewing machine, however, the foot won't go down properly and actually when I press the lever the foot goes down in slow motion but doesn't then grip the fabric. Anyone got an suggestions on how to fix it? I don't want to get rid of it because it is otherwise a good, solid machine.