czemu to zdanie jest poprawne

kurcze znalazlem zdanie w ksiazce do gramatyki (lol) :
I wonder when he will pay me back.
Ja raczej bym pwiedzial : I wonder when he pays me back ,przeciez to time clause Bardzo bylbym wdzieczny za wyjasnienie sprawy,z gory dziekuje

If 'when' means 'kiedy/gdy' then it is used in the time clause. If 'when' means only 'kiedy' then it is not in the time clause that 'when' is used. Cf.

I'll phone you when I get back home.
Przedzwonię do ciebie kiedy/gdy wrócę do domu.

I wonder when he will pay me back.
Zastanawiam się, kiedy (NOT gdy) mi odda kasę.

Thx

I'am shure that you are right ,but I see no difference beetwen 'kiedy' and 'gdy'.If you could explain it more complexly I'd be grateful

To nie jest time clause. to jest pytanie w mowie zaleznej.
Zmien 'when' na 'how' albo 'why'
W pytaniach z when nie obowiazuje zasada braku 'will'.

Taki kolo, you've noticed that there is no difference - that's it! That is what I wanted to explain to you - if you have 'when' in a sentence, where you can translate it into 'kiedy' or 'gdy', then you can be sure that it is a time clause and therefore you aren't supposed to use a future tense after it. If 'when' can only be translated into 'kiedy', and not 'gdy', then it is not a time clause and you can use a future tense. ;-)