As a native English speaker, I'm naturally highly fluent in English, but not other languages. My planned method for translating is basically to run it through Google Translate and then "clean up" the results. Just wanted to put that out there before I actually try to translate anything, in case that's against site policy or something. So if that's okay with the mods, I'll translate just about anything.
Welcome. Frankly, I'm higly dubious of this method, I feel like there is still the chance of major fuck ups. Not sure it's against the site's policies though.
What I am sure about is that you can safely help by reviewing other people's works, searching for sentences to rephrase in a more suitable fashion or suggesting corrections.
Unless you're already decent at the other languages to some extent, that's not going to work, and even then it won't be on the same quality as someone who's fluent in both.
I've done this translating SCPs from Polish, Spanish and French. Though the risk is not to understand phrases, words with multiple meanings, spelling errors, puns etc.
Another problem is, that it's hard to rephrase. Different languages have different ways to build and connetct sentences. So expressions spaning over multiple sentences can possibly be phrased completelly different. Google translates everything literally though.
But in the end, it's possible. I'd say try it and we'll see if the result is usable. I mean, many translators here don't speak English well. How bad can it be?