I happen to be learning German and Latvian right now. The way I'm approaching them is to find easy-level texts (https://www.nachrichtenleicht.de for German, children's books for Latvian), and reading a couple of paragraphs. Whenever I find a word I don't know, I use Google Translate, and add it to a custom Anki deck. Then I practice vocabulary every day.
This is a slightly more structured way of how I learned English back in the day (my English improved tremendously by playing Monkey Island, especially trying to understand the pirate insults).