I believe other sources include UN documents, which are translated into even more languages, and then there are a bunch of combined corpora like https://opus.nlpl.eu/ which contains hundreds of languages as well.
The obvious downside of this, of course, is that translated text often ends up quite official and stiff. Great for reading news, translating speeches and reading papers, not so great for day to day conversation. There are corpora for more practical, specific use for a few languages, but they usually only come in pairs.
I don't know how services like Google Translate work now, but through experimentation you used to be able to see how the translation matrix went through English first when you translated between two other European languages. You'd put in a word for which the source and destination language had specific words, but for which English only had one single word, and you'd get a mistranslation every time. The shorter the sentences, the more likely the translation service would get it wrong.
I just found out this can still be replicated on Google Translate, actually: the Dutch word mees (tit, the bird, aka titmouse) and the Dutch word tiet (tit, slang for human anatomy) both get translated into French as mésange, the bird, when you enter them each on a new line. Add more words for context ("wat een grote rieten" vs "wat een grote mezen") and the translation corrects itself.
I don't believe the French word mésange has any direct correlation with mammal anatomy, so clearly the translation matrix involves the English language, or af least one with similar ambiguities. This is why you can't rely on Google Translate if you're just looking for the translation of a single word, especially if you're translating between languages other than English.