So there are even 3 words for only: so, somente and apenas. Is there any difference or are they interchangeable?
No, they are the same. But "só" also means "alone"
I'm a native Spanish speaker and in Spanish 'apenas' means 'barely'. How do you say "He barely tries to keep people safe" in Portuguese?
estou de acordo com o senhor
Ele mal tenta? I am not a native Portuguese speaker though. Apenas carries the meaning barely in Portuguese as well, but I do not know how to tell without more context.
Actually, people also say "malemá" :S I avoid using this, but as "mal", it shows the person is not willing to do somthing.
"barely" fits way better than "only" in this case.