It is always difficult to determine who will win the Champions League title, especially when the season has not started. Manchester City certainly have a chance to repeat their success, but to defend the Champions League title then I think it is the most difficult challenge for any coach. Pep Guardiola is expected to keep his chances good, but all the teams that will be competing in the Champions League will also be pushing for the title.
Instead of the Champions League, the Premier League has always provided Manchester City with the opportunity to repeat their achievement to win the title. Since Pep Guardiola became Manchester City's head coach, they had dominated the premier league for so long. They recently succeeded in winning the championship for the first time. They won't be able to repeat it consecutively, in my opinion. Only Real Madrid has been successful in winning the Champions League on multiple occasions. I'm not sure if Manchester City will be able to accomplish their goal of winning the Champions League title by the end of the next season. That's the puzzle we can't tend to solve until the champions league match start
Every season, of course, there will always be improvements in terms of players to the strategies used and I think Manchester City is also doing the same thing in order to retain the Champions League title. Indeed, it must be admitted that it is very rare in the last 10 seasons that a team has been able to win this competition back to back except for Real Madrid and of course this will be a challenge for Pep Guardiola and his players to be able to prove this even though it is quite difficult.
Real Madrid has always had the magic to do that and even though they had difficulties, they were able to reach at least the semi-finals. The puzzles you mean are things that cannot be explained with certainty because they all refer to the initial competition so that each missing puzzle can be solved. Either Manchester City or Real Madrid still have the puzzle pieces before they finally get them back into a whole.