Antwort auf: Ich habe Probleme mit meinem Trezor und den Transaktionen! Bitte helfen
He is probably not even using his Trezor seed but the software wallet on his phone which has a totally different seed and is a so called hot wallet. You can verify that by comparing the wallet addresses of your Trezor and your phone.
For example, Metamask is a software wallet that you can connect your hardware wallet to. The 2 are totally different wallets, but some folks forget about that.