None of the other replies I saw seems to be universally true.
I find that Excel is rather erratic on this topic. I work with a laptop originally set-up in German and English as my default language and depending on the tasks at hand may switch often, hardly or not at all.
I find that sometimes the shortcuts will work in German only, sometimes in Einglish only.
Usually related to the current language selected.
However, sometimes they do not work at all, until I restart Windows.
If I do, they then work in the language that I first used (possibly first used while saving a file) in Excel.