Sebastian Haller has joined Borussia Dortmund and is back to Bundesliga after a fairly decent run with Eintracht Frankfurt and after being kinda poor with West ham. Revitalized his career at Ajax with 32 goals in 50 appearances. With much more attacking prowess that Borussia brings. He should thrive there.
Borussia Dortmund are used to losing some of their professional players because this club is often dubbed as a printer of new players who have high expertise, so because they often get offers to buy players with very high nominal, so it has become a normal thing for them.