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.
In Europe, we have serious trouble with weather for many teams specially from South America which give good advantage to European teams, and they were able to qualify for semi-finals without any team from South America but now here in Qatar no advantage for any team as most probably weather conditions are going to favor all teams or may be more suitable for South America instead of Europeans so here competition is tough and Argentina and Brazil both can do much better than Russia 2018.
Currently, mostly European teams are unpredictable and have no momentum which is going with Brazil and Argentina, so I am feeling these two and France and Germany can go into last four.