Sometimes the European Cup is the scene of more exciting matches than the World Cup. France and Germany are among the top teams in tournaments, but Germany has been out of shape lately. Especially after their bad performance in the world cup, they will want to be champions in the European championship.
I highly doubt that Germany can become the European champion next year. Of course they would love to do it because their country is the host, but wishes are one thing and reality is another.
Ideally Croatia should be able to top the group, but you can never predict matches involving Turkey. They are such a volatile team. On their day, thy can defeat strong teams such as Germany. And on other days they will go down to teams like Latvia and Armenia. BTW, I am surprised that Belarus is taking part in the competition. They were banned by FIFA, because they were seen as too "close" to Russia. I am glad that at least UEFA took the right decision here, by distancing sport from politics. They are placed in Group I, along with Switzerland, Israel, Romania, Kosovo and Andorra.
Croatia is similar to Turkey in that sense. They are known to win against the biggest teams like England and France only to lose the game against some much weaker team. For example, at the start of the Nations league, they have lost the game against Austria 3-0. I don't consider Austria as a weak team, but I think that Croatia is much better team and losses like that should never happen. But everyone has a bad day once in a while. It's better to have a bad day at the start of a competition then in the final game