I do not run in the summer - I would expect this to be either "Io non corro in estate" or "Io non corro a estate" (based on another example I saw where "a" translated to "in". So I am a little confused by this translation.
Prepositions in one language don't always match one to one in another language. In other words, an English preposition (eg 'in') might have a few different translations in Italian depending on the context (eg the "d'" in "d'estate", the 'a' in 'a Roma', the 'in' in 'in Italia'). I've just tried to memorise when to use each but perhaps there is an easier way that someone else knows?
this is a little bit helpful, when I can find the other link I know of I'll try an update this.
But to clarify for everyone "I do not run in the summer" and "I do not run in summer" are interchangeable :)
Listening incomprehension: The last word clearly started with a "b", had no clue what it should have been.