It will take time for Ten Hag to make changes at Leverkusen because after all the departure of Xabi Alonso has made this team have to go through adjustments. The target next season to compete for the title but it will be difficult to achieve if Leverkusen does not strengthen the team with the swelling of several important players. Everyone associates Ten Hag's failure at Manchester United and maybe many people are pessimistic that Leverkusen under Ten Hag's coaching can be much more successful. Anything can happen but we need to give him time and trust him because who knows he could repeat the success he had at Ajax.
I don’t think Ten Hag will be able to seriously challenge for the Bundesliga title next season. Alonso showed this year that when Bayern worked with Kompany, they became much stronger, meaning Bayern overcame their crisis and competing with a team like that has become extremely difficult. After Alonso’s departure, the situation could get even tougher. Plus we will need to see how well they manage to keep their key players and how Ten Hag handles the transfer market. He is a good coach and he built a strong reputation before his time in Manchester, but I am not sure that is enough for Leverkusen to win the title again.