I got a vw. When I bought the motor was fine. I spun it once or twice. Then it locked up. What could cause it? Nd how can I fix it?

I think you'll have to do a teardown to find out why it's seized. You don't say how you put the Marvel in the motor, but you may find it more helpful to inject some into the spark plug holes to lube the piston rings. In fact pull the plugs and try spinning the motor again by hand or with the starter, the lack of compression may make it easier. However, your engine might be due for a rebuild.

I put it through the plugs. It still ain't help. I guess ima rebuild it