I disagree with your opinion because Haaland and Bellingham played for Dortmund before they were 20 years old and were sold, but Guirassy is 28 years old. Right now, Dortmund buys him not to sell him, but to have him play as a striker in the team. Getting value from him may be more important than selling him, just like they transferred Haller, but Haller was unlucky and suffered an illness. I hope Guirassy will benefit from joining Dortmund
Interesting, to be honest I didn't think Dortmund would be interested in bringing in another striker under the tutelage of the new manager, namely Nur Sahin. Moreover, Dortmund has several players assigned as ST in their squad, namely Haller, Fullkrug and their young striker Youssoufa Maukoko. So if Guirassy is successfully brought to Signal Iduna Park, this means that maybe two of the previous center forwards will be released by Dortmund. This is just my personal opinion, regardless of Dortmund's plans in this summer's transfer window. Understandably, at this time I am not very active in looking for the latest information.
Talking about Guirassy, the striker who played for Stuttgart last season, seems to be the best option for Dortmund amidst his team's difficulty in scoring goals in the previous season. Guirassy was quite impressive with Stuttgart, he scored 28 goals in the Bundesliga. Maybe Dortmund plans to start the season with an impressive performance, apart from bringing in a striker they are also focused on defense. despite the latest reports I read, if Dortmund are just one step away from signing Serhou Guirassy. well, I hope that if Guirassy wears the BVB jersey in the season that will start soon, he can play as well as when he played for Stuttgart. Maybe in this way, Dortmund will join in tight competition in the race for the League title.