Leipzig have the biggest question mark for me (along with Leverkusen). I think they might struggle and have a fight on their hands for the champions league spots.
Timo Werner is going to be a massive loss and they may come to regret not making Schick's deal permanent.
Hwang has come in from Salzburg but his goalscoring output (in the Austrian league) is not very inspiring and Sorloth may struggle to match his Turkish league exploits when he signs.
Monchengladbach have had the best summer as they did not lose a single star. They have also added two players (Lazaro from Inter and Hannes Wolf from Leipzig) who manager, Marco Rose, knows very well from their RB Salzburg days.
The big issue for me is lack of a clear goalscorer in their team. Last season they benefited from having 4-5 players chip in with 10-15 goals each but you cant expect that to happen every year.
Leverkusen also have two massive holes in their starting XI from the departure of Volland and Havertz.
They have signed Schick who in an ideal scenario would be a good replacement for Havertz but they will certainly miss the industry, physicality and link up play of Volland unless they can get someone in before the deadline day.