Hi snapey and welcome,
for me all the shifts are the same tbh.
First off would be to get the gear linkage alignment check done, theres a chance its been messed with and 2nd happens to be the gear you cant get. (are 4th and 6th on the same plane OK ? )
Next stop would be looking at the gearbox ?
Theres also the chance its clutch related (i.e. its not disengaging when you go for second) , but odd behaviour would happen in all gears I would think.
Im sure someone with more knowledge than me will be along soon ........
p.s. I would also do searches on other forums for related issues
Let us know how it goes, I'd get a local VW specialist on the case if you can
, pref not a dealer (you in warranty?)
John