It's the number of outgoings that intrigues me regarding Dortmund's transfer activity. At left back, if they let go of Schulz, they'll only have Guerreiro and Schmelzer to call upon unless they plan to use Thorgan Hazard there more often (can Mateu Morey also play there?).
In the midfield, whilst they'll have Bellingham coming in, there's also the case of what could happen to Weigl (stay or leave?). At this time, the only midfielders who'll offer them anything defensive are Witsel, Delaney, and Can (if we assume that Dahoud is leaving). Can can also play at the back line and might be playing there more often given that Piszczek will be in his final season. If Meunier keeps himself fit like Hakimi did, they'll be fine at right wing back.
Will Bellingham be playing so often for Dortmund? I can't say for certain though pre-season certainly does indicate that he'll have a place in the first team.
First of all: Bild's hit lists are best taken with a grain of salt.
Schmelzer in all likelihood won't play a significant role anymore, Morey supposedly can play some LB, Zagadou as well, but I would assume that they bring in a fresh face if Schulz gets sold.
Weigl left for Benfica last winter.
Witsel, Delany, Can are three quality players for 1-2 defensive minded CM spots. By Dortmund's standards that's reasonable. I can't predict how often Bellingham will play, but with Dahoud on the outs and Brandt being a bit sloppy for a CM role I could see him end up as the first choice should Favre want to have a ball carrier in CM or as one of the first substitute options when the team needs some more attacking edge. Knowing him he will probably rely on established options at the beginning and ease in the young players via substitutions, what happens then is up to them.
Given that Reus can't catch a break with his injuries they are about to strengthen their depth with the Reinier loan and I could maybe see them loan another attacker if Favre wants to switch back to a 4231, but they had a good squad last season and they've basically kept it together, so there isn't really any pressing need for adjustments or upgrades.