Can I learn more than one language on Langua? And does it cost more to do so?

You can switch between languages and there's no extra cost for learning multiple languages.

You can go to Settings and change the language, then save (it'll autosave if using the mobile app). At present, if your level varies by language, you will need to adjust it manually (in future we'll see if we can save the level to our database for faster switching).

Due to the way Langua is set up, if you don't want to bother switching language each time, you can simply return to past conversations via the History page. There, you'll see chats from all languages. If you open one, the settings from the chat will override your account settings. This means that you can return to a previous conversation without updating the settings and it'll still work - translations will be in the right language. If you save vocabulary, it'll be saved to the right language.