Khan Academy courses in French, Spanish and Portuguese
You can do free online education through Khan Academy at https://www.khanacademy.org/ in English, Spanish French and Portuguese. A lot of their video content is in English right now, but with optional subtitles. This means you can listen in English while watching the subtitles in your learning language. This is very helpful because they delve into much more specific topics than Duolingo does. For example, if you are learning French for business and you work in finance, you can take finance courses in French through Khan Academy and learn the associated vocabulary.
There are pages set up for non-English speakrs, too. For instance:
gives examples of their naming scheme for French and Russian. There are similar pages for Spanish, Italian, and others.
It's not about languages. It covers all kinds of other contents BUT you can change the interface language to English, Spanish, French or Portuguese. That means you can e.g. brush up your biology knowledge in French. It's just like watching movies with subtitles in your target language. Just more educational than most movies.
And it should be really useful to learn specific terms that aren't taught on Duo. Maths, biology, finance, arts, programming... Whatever!