Ok, thanks a lot. The problem is "the fire" hadn't been introduced into the context, but it was used with the definite article. And in the grammar box before that exercise was mentioned that in most cases we use the definite article after prepositions. So I thought that was the case (after the preposition "by"). And in the following sentence it was said "I was born in a cold part of Canada". So, I don't really get if we use "a" or "the" in this sentence (1. after the preposition 'in' - so we need "the", 2. on the other hand, it is not a specific place - so we need "a"). Articles after prepositions - that's challenging!