I think the first team to be relegated from the Bundesliga is Holstein Kiel. They are a very weak team, especially their defensive line is very weak, they concede a lot of goals in their goal. They lost 2-4 in front of Frankfurt in the match that just ended.
They got 1 point ahead of Bochum last week, but Bochum is also a weak team. If they continue like this, they won't even get 15 points until the end of the year.
Despite it being too early to judge which team will be relegated, I agree with you that Holstein Kiel may very well be the first team to be relegated at the end of the season with their poor performance. In just five matches, Holstein Kiel has a goal difference of -10, which is very bad. Honestly, it is clear that their defensive line is very weak, as opponents can easily score many goals against them in each match.
Holstein Kiel needs to focus on fixing their defense; otherwise, the efforts of their attackers will be wasted. Their attacking line is trying because they do manage to score goals, but if attackers are putting in effort, defenders need to work harder so they won't concede so many goals. Currently, Holstein Kiel is at the bottom of the table, and with this performance, they may remain there until the end of the season unless something is fixed.