In your settings, you can set your preferred languages - since you're on lemmy.world this link should take you there. You can hold control down to select multiple options if you're on desktop (and mobile should have a selection box pop up).
Though be sure to keep "undetermined" enabled, otherwise a lot of stuff will vanish. Also note that this only works for posts/comments where people have actually selected the correct language (if someone posts something in German, but marks it as English for example, it will still pop up).
In your settings, you can set your preferred languages - since you're on lemmy.world this link should take you there. You can hold control down to select multiple options if you're on desktop (and mobile should have a selection box pop up).
Though be sure to keep "undetermined" enabled, otherwise a lot of stuff will vanish. Also note that this only works for posts/comments where people have actually selected the correct language (if someone posts something in German, but marks it as English for example, it will still pop up).
Undetermined has a lot of English content, but also holds all the "undetermined" content.
While a lot of content disappears when disabled, I think this is exactly what OP asks for.
An alternative would be to block communities from non-English Lemmy instances, but that isn't foolproof either.