Remove the pan and check for metal debris, probably failed internally.
The transmission is slipping/dying, take it to a certified mechanic..
3 forward, 1 reverse
A Super Beetle with a manual transmission has four forward gears and one reverse. A Super Beetle with an Autostick transmission has three forward and one reverse.
your problem is the transmission. you need to replace the transmission
It's the main drive gear mechanisms in the transmission.
If this is an automatic transmission, more than likely the transmission is on it's way to the junkyard. Usually failing transmissions lose reverse first, then the higher forward gears - last will be the lowest forward gears.
the forward gear clutch pack is worn out. the only solution is to get the transmission rebult.
it grinds grains and connected to gears
If your stickshift makes a whining sound in gears, grinds when you are trying to put it into gear or if it slips out of gear you know it is going out.
If it has an automatic transmission, it probably needs to be replaced or rebuilt.
the clutch or clutches in the transmission are bad,even if changing the tranny filter helps the forward gears will not be right and quit again
The forward pump is shot or the throttle has a blown gasket