not just some matches, if you think some are fixed then I would assume most of them are, it's like they gave Italy the Euro but they had to not qualify for the world cup, anyways the final you mentioned with Portugal and German seems tough to happen, I'm expecting a Latin team to win the world cup this year since it's been 19 years when the last one won it which was Brazil, they are the favourites for me unless Argentina made a surprise.
Last time (2018), the world cup was held in Russia and none of the CONMEBOL teams managed to qualify to the semi-finals. France, Belgium, Croatia and England managed to find a spot in the semis and all these teams were from the UEFA (Brazil and Uruguay were kicked out during the QF stage). It is clear that weather played its part in 2018. But this time, that won't be the case, since the weather in Qatar will be very mild during November-December. Also, both Brazil and Argentina have the momentum at this point.
Brazil and Argentina have good momentum only on their continent. Nobody knows how they will play against European teams. I watched the qualifiers and these two favourites are definitely good, but the other teams have shown poor quality football. I think it might be a consequence of the pandemic. That's why Argentina and Brazil are only good on paper so far.