In your profile on lemmy web ui you should be able to set a language.
Problem is a lot of posts just don’t set a language. If you filter to english only you’ll filter all the english language but undefined tag. It’s frustrating but is what it is
I just block the prolific foreign language communities and scroll past the remaining ones I don’t use all very often, so not a big issue for me
I just manually block communities where the default language is non-English.
Just learn the languages!
Honestly though if you’re seeing enough to bother you then just start blocking those communities. I’ve only seen a few communities in German or French and like one Hindi instance
I personally understand enough français to be able to mostly get the content, try to discern the wild German memes, and just scroll past the Indian content that rarely comes up
