Is there a way to block foreign language communities from all? I don’t have anything against them, I just can’t understand them

Talking about Web View: In your settings, you can select which languages you want to see. This is a multi-select box! Recommendation: Select all languages you want to see, plus "Undetermined"! Do not select languages which you do not want to see. This will block posts and comments in unselected languages.

If you additionally want to block whole communities, you can do so at the same place where you can subscribe. The block button is hidden while subscribed.

If you use one of the apps they usually have an option to block a person, community, or instance. Not sure if there is a shortcut or setting for foreign language you probably just have to block them as you see them.

I like it! I like those Germans and all the ich memes. Jajaja