Hello. I'll use orange for corrections, and teal/green for style suggestions and alternatives:

I'm just watching the World Cup in Brasil. Netherlands vs. Spain. The seats are fully occupied by supporters of both teams. The commentator said some of them (the group of Netherlanders / the Dutch side in particular) have travelled to be at the matches for the whole five months / have travelled out to be there for all five months of matches. 

What is amusing me in the matter, / What amuses me about the matter/situation, is where those numerous people have got so solid an income / got such a solid income that they can exist without any work for such a long while/time? It seems like millionaires are around everywhere / are everywhere. Who said the world's financial crisis is on the march out there? / ... marches on out there?

Five months?! Haha