If you wanted to say "It is not certainly my problem" (i.e. It is not certain that it is my problem) how would you say that? Is there any way of doing it just by moving the "certamente"?
There are a few words that come from Greek, like problema, that have an -a ending but are masculine. You just have to sort of remember them. Others I can remember are dilemma and programma.
Panorama is another one that I came across recently. Hands up all those who hate masculine nouns ending in a? {Shoots own hand up}. Yes, I got caught by this one too.
That would be a semantically correct interpretation of the sentence. But pragmatically, most of the time the è has problem as subject.
When someone wants to say to say "he is certainly not my probelm", they would surely use Lui explicitely.