If the player was set on returning to German was the correct decision. We sold him on deadline day & could have signed a pre agreement 120 days later. Had to renew or sell.No it wasn't. He had a year on his contract. Hence why Werder Bremen paid about £5 million for him.
https://www.fourfourtwo.com/news/arsenal-offer-gnabry-new-contract-wenger
https://en.wikipedia.org/wiki/Serge_Gnabry