Questions & Answers about Eu arrumei só o sótão.
Why is só placed after the verb here instead of before it?
Placing só directly before o sótão specifically restricts the focus to the attic, meaning you tidied the attic and nowhere else. If you said Eu só arrumei o sótão, it could mean the same thing, but it could also mean that tidying the attic is the only action you took (for example, you didn't paint it or fix the roof). Putting the adverb right next to the noun phrase makes your exact meaning unmistakable.
Could I use apenas instead of só in this exact spot?
Could I put só at the very end of the sentence, like we sometimes do in English?
Does arrumei imply I scrubbed and washed the attic?
Not necessarily. arrumar means to tidy, organize, or put things away. If you actually washed the floors and wiped away the dust, you would use the verb limpar (to clean).