Translation:I spoke English worse than you then.
My answer of “I used to speak English worse than you”, should be accepted. This is very commom phrasing in the US by native speakers and likely in Great Britain as well.
You are missing "then" "at that time" "back then" or some other equivalent of "tehdy".
I am not sure whether we don't translate "used to speak" as "mluvíval" (an iterative/frequentative), I have to check that first.