Aston Villa interested in Julian Ryerson

Aston Villa could see him as someone to bolster their defensive department for the next campaign as they hope to be in the Champions League. He may also have been identified as potential competition for Matty Cash at right-back.

Dortmund has weakness in their full back positions, Ryerson has been a solid addition that really made a difference to their defense and with all likelihood of Wolf and Morey leaving at the end of the season, he is the only right back left in the team.
Add to that the fact that Ryerson can play left back and with Bensebaini not doing well on his first year there and Maatsen on loan with a rising market value to a point it's unlikely Dortmund will buy him, it will be just stupid for Dortmun to sell him.
That said, with the likely change of manager at the end of the season, anything is possible.

I would sell Bensibaini ,Can , Moukoko and if funds needed maybe Byno-Gittens and Reyna.
Brandt and Malen can bring lots of funds but they are more vital to the team. However, their preformance is not always steady.