"I can buy everything!"
Translation:Mogę kupić wszystko!
Mogę kupić wszystko actually sounds more like: I am so rich. Hurrah, I can buy everything. Mogę wszystko kupić is rather: ok i am in the shop and i can buy there everything what i need to buy. but the difference is very very subtle
Both are fine actually. Since Polish is based a lot on inflection the actual word order in most cases does not matter, the word endings make the meaning and word relation. Just that it does not sound "natural" when it is changed. I guess the correct answer is usually the most common way of saying it. Nonetheless I can see someone saying both "mogę kupić wszystko" and "mogę wszystko kupić", and both mean the same.