Union Berlin was my favorite team this season and I was even hoping to see them at the top of the table and racing with Bayern Munich until last week when saw them having a bad performance because of having not enough potential for the rest of the season.
I think Union Berlin could have much better transfers and they could hire better players to help them in this situation.
https://en.wikipedia.org/wiki/2021%E2%80%9322_1._FC_Union_Berlin_season#Transfers
For a new team in the bundesliga with their first achievement to enter the top 4 of the standings, this is very good, especially Union Berlin will appear in the champions league for the first time too. So I think that rather than being able to compete with Bayern Munich, which consistently wins the Bundesliga every season, it's better for Union Berlin to focus on consistently competing in the top 4 in the next few seasons or at least not get out of the mid-table zone because as a new team they have to prove to the fans that they really deserve to be in the bundesliga.I think Union Berlin could have much better transfers and they could hire better players to help them in this situation.
https://en.wikipedia.org/wiki/2021%E2%80%9322_1._FC_Union_Berlin_season#Transfers
Regarding players, maybe they need several players for attack, midfield and backline so they can have a stable performance for next season. Each line requires at least 1 to 2 new players so that player rotation can run more smoothly.