Do you think there is a mess with matchmaking?

Yes I do.

Actually, it is not fun at all that it happens several times every weeks.

Did my level drop in a single day? Did my opponents become stronger in a single day? Do these results really correspond to my level? Are matchmaking, elo ranking and a player’s level correlated?

Do what you want about this topic, it is just a tiny result of months of annoyance.

Streaks happen. If you're off one day, it may be a lot easier to miss things and if you keep playing in that mindset, you might keep losing. Sometimes, you're playing well. 

But your rating didn't change very much during those streaks. You won 8 games against closely rated opponents. Your rating went up by 55 points.  Then you lost 7 and it fell by 48 points.

The result ? You won 8 and lost 7 and your rating didn't change very much.

Yes, I think that there is a serious mess in the chess.com pairing system. It is mind boggling that players rated well below 1000 win arena tournaments, but never face a strong opponent during that tournament.

That's the design of Arenas. It's meant to pair players relatively close in rating and provide anyone a chance to win an event, regardless of rating.

 i agree  i don't agree with martin_stahl they don't closely pair you -- the system is not working for me at least -- i rather not play then play some one who way smarter than me -and i can only void a game so many times -- then  they give a warning about finishing games -- not sure what the answer is but better system is needed --

My quote was about arenas, where that is the case. For random pool seeks, it depends on your settings.

https://support.chess.com/article/1962-how-do-i-choose-what-rating-my-opponents-are