Problem bei der Rückgabe des E-Bikes an Decathlon.

Hi guys. Recently I ordered an e-bike from Decathlon. I received the package from the courier, the bike was very scratched and damaged in many places and the package was taped. I decided to return the package. The courier arrived. He said he had a package to pick up, scanned the old code from the package and took it. I've been waiting for a month, no information about the package, no money. I've called DHL and Decathlon many times, they don't know anything, everyone tells me to wait. Please help. I don't know what to do. I just lost 2.5k€!?