Mainz have signed former Germany international goalkeeper Rene Adler on a two-year contract.
Borussia Dortmund have told Barcelona that Ousmane Dembele is not for sale this summer amid reports the Catalan club have held talks for the player.
Darmstadt completed the signing of United States youngster McKinze Gaines from Wolfsburg on Thursday.
Arsenal have confirmed that forward Takuma Asano will spend a second season on loan at German club Stuttgart.
Holger Badstuber is seeking a new challenge outside of Bundesliga when he leaves Bayern Munich this summer.
RB Leipzig have reiterated they won't allow Premier League targets Naby Keita and Emil Forsberg a transfer away from the Zentralstadion this summer.