Bleachbit seems pretty good, but I don't know how to delete all language package except for English. Or should I do that in the terminal? I don't know the command for that is so.
Exactly what language packs are you wanting to remove.
If the language packs are in the browser then you should be able to remove them through extensions.
You should also be able to remove them through Synaptic Package Manager by ticking search and entering language-pack and scrolling through the ones installed and then tick the box and follow the prompts.