Yes. Before nouns we have prije on its own and the noun is declined in the genitive, whereas before verbs it has to come in the expression prije nego što. The verb is then conjugated.
The same root gives us the noun ulazak (entrance, the act of entering), and here is a headline that has it after prije:
Kako da sredite finansije prije ulaska u 2020.
how that you.get.in.order finances before entrance.GEN in 2020
How to get your finances in order before entering into 2020.
Compare your sentence:
Popravlja kravatu prije nego što uđe u ured.
he.fixes tie before he.enters in office
He fixes his tie before going into the office.
This is fairly common in Croatian, a similar example that comes to mind is umesto + genitive noun and umesto da + conjugated verb.
Pogledajte kako dron šeta psa umesto vlasnika
look.at how drone walks dog instead.of owner.GEN
Look at how a drone walks a dog instead of its owner.
Umesto da pomogne građanima, on bi da se igra politike
Instead.of that he.helps citizens, he would that (reflexive) he.plays politics
Instead of helping his citizens he wants to play politics
Generally it's not typical for Croatian to allow prepositions before verbs without being accompanied by some conjunction, in the above cases nego što and da, although it does occur in some calques from Italian/German: nešto za piti (something to drink; literally "for to drink") and za poneti (takeaway; literally "for to take").
As for the literal meaning of nego and nego što, nego can also be used for comparisons, besides the meaning you mentioned:
Osećam se bolje nego prije.
I feel better than before.
Then we add što so it can be followed by a conjugated verb:
Osećao sam se bolje nego što sam očekivao.
I felt better than I expected.
Last edited by Saim
on 2020-03-21, 16:46, edited 3 times in total.