Its part of a line from the song Rad by Faun:
Dreh dich nicht
Um wenn du
Nicht willst das
Man dich sieht
I understand all the words, but I don't get what this 'um wenn' construction is. The parts I can make out translate as such:
Don't turn around
don't want that
(some)one sees you
Note that this is a literal translation. The latter part would probably be better translated as: 'You don't want to be seen'.
I know what um and wenn mean. Um has several translations. It can be either a preposition or a conjunction (which I'm guessing is its use here). As a conjunction, it normally means 'in order to'. Wenn is the word for 'if' (though sometimes its used where in English we would use 'when'). I don't get why these two words would be next to each other like this. Why would you have two conjunctions in a row?
Also, I've tried to look for this on wordreference's dictionary. I didn't get a result for this specific construction. I'm at a loss as to where else to look.