When I looked up the stats i'am quite shocked. At Hoffenheim he scored 16 goals. He played 33 times last season. This condition means he is able to play regularly at Hpffenheim. In addition, at the age of 21, Dortmund invested in promising players. But when compared to Haaland Beier, it seems to be shorter. In addition, the body is slightly smaller. But at that age he is still very capable of improving muscle mass. Next I have to see his game if the season has started.
But no one knows the future and maybe Beier will also have the same fate as Haaland or other strikers who can improve their careers at top European clubs. What is certain is that now the main path is open by joining Dortmund and if he stays at Hoffenheim maybe no club will see him. We know that Dortmund will always be a place of observation for scouting teams from other teams and of course from here it can always produce stars in the future.
There are many good strikers who have short statures such as the legends Inzaghi, Owen, or even David Villa, but indeed to compare them Beier must prove his achievements consistently for more than 5 years and must play with a big club. Well, muscle mass is very important and if he knows that is the main capital that he must have before being excited with adrenaline as an experienced striker.
With how Dortmund ends up with getting good players and turn them into great players and sell those players we can assume that Beier could end up like that as well, it wouldn't be really that weird so it can be something totally possible.
We cannot really expect the same all that easily, so we can't really assume everything to be working that easily, it can definitely be something that may fail in the end as well. He might turn into something that could be either very very profitable for them and make like 50+ million profit, or it could be something not worth it at all, it may not work that well at all.
We cannot really make heads or tails with these stuff because we can't see how things will turn out. So all in all we can assume that Beier reached to the best place he can be to improve himself as a young player. We should not be really making predictions about this yet, but we will see how the season goes, if he scores 30+ goals then it will be great.