According to the schedules first fixtures of Champion league will be starting on September 17th - September 19th and according to the list i was found some interesting matches which we can called those are big matches such as
AC Milan vs Liverpool
Manchester City vs Internazionale Milan
Atalanta vs Arsenal
An interesting fact about Liverpool when playing against Milan is that Milan have not been able to beat Liverpool since 2008. It's funny because Milan have not been able to beat Liverpool for more than 15 years, which means that Liverpool have this historical advantage in games against Milan.
https://livescores.biz/h2h/liverpool-cf-vs-milanLooking at the current situation of both teams, Milan has been an unstable team for many years, but at least they have managed to get through the group stage of the European Champions League (in the old format) while Liverpool have not done very well in the European Champions League in recent years. They were champions in the 2018-2019 season
Klopp's Liverpool get their reward
source: https://www.uefa.com/uefachampionsleague/history/seasons/2019/but then they have not been able to perform well,
Even with the same coach and most of the squad. Now with a new coach they are playing better, they have had a good defense and honestly I see this current Liverpool with a good chance of winning the European Champions League again. But I don't see Milan being able to win the European Champions League, they were a very strong team in the years 2000 - 2010, they won the Champions League in the 2006 - 2007 season. Today they only make average signings, it doesn't even seem like a team that had Ronaldinho, Kaka, Cafu, Seedorf, Dida. Today they have a very low level squad.
About City's game against Inter, it will be a balanced game. Inter are strong.
About Atalanta's game against Arsenal, it is a difficult game to predict, Arsenal have been terrible in the Champions League