"He speaks English badly."
Translation:On źle mówi po angielsku.
Polish has a relatively free word order. Please forget the idea of a "free" word order. It's simply not true and such an idea makes some people write totally bizarre sentences.
Having said that, this sentence had correct options missing (ones posted by AndRL82), which I've now added.
"źle" is the default version, it should have been accepted (well, with a typo).
"kiepsko"... well, the words for "bad" are quite problematic in Polish. Yes, "źle" is the direct translation, but I'd also probably go with "kiepsko". Even though it's colloquial. Still, it very often sounds better than "źle". Similarly a form of "kiepski" often sounds better to me than "zły" (when it means 'bad' and not 'evil' or 'angry').
"kiepski" is like... "baddish". "kinda bad". "not really good". But... it's just often closer to what you want to say. "On mówi źle po angielsku" is more like "His English is just BAD. SO SO BAD." "On mówi kiepsko po angielsku" is more like "His English is... well, not that great". It's hard to pinpoint the exact meaning. So "źle" is stronger, but sometimes it just seems too literal and... too much.