I wrote: Futebol é o mais popular esporte no Brasil.
And was wrong, but I can't understand why, could someone please explain?
The order is wrong. Noun + adj, specially for superlatives!
There was another sentence in this very same exercise where the order was different with a superlative.
Acompanhe em directo as melhores jogadas e todas as notícias sobre desporto, actualizadas ao minuto. This is portuguese, so "desporto" was perfect, not wrong.
one would never use that in BR-PT: directo, desporto, actualizadas, ao minuto.