There are only 4 bolts that hold the seat down. on each leg at the floor you will need to pull off the trim piece. Then the bolt will be exposed and you can remove it and the seat will come out. Be careful; of the connectors so you don't break them. Dis-connect them before moving seat much. Examine gear and try to plug seat back in or remove motor and turns by hand to see why it is not locking.

Is there tension on the release handle or is it all loose / no spring action?

1999 is a cross-over year here in North America... what body style Golf? A3 or A4 (mk3 or mk4)?

Although similar, the design is different.... both require the seat to be un-bolted at the front center, plastic trim to be removed
at the back and then the seat is able to slide backwards to exit the retaining tracks and be tilted out (not bolted at 4 corners).

I might be able to find some Euro info (if that is where you are).

Thomas

exovds is a Volkswagan expert so follow his inctructions. He will not lead you astray.