Hello everyone, I found the solution, albeit by mistake.
First of all, if you already have a manager career, forget about it, sorry. It is a solution that allowed me to play my 15 created players in this way for 4 seasons and I can say it is easy.
First of all, go to settings and transfer the players you have created or will create one by one to a different team, or create them again. My recommendation is to delete created players and then recreate the players you want. Each player you create should be in a different team. The players you create should NOT be in the same team. Then, in the settings section, transfer the players you created to Free Agents, that is, make them free.
Then create a manager career. Then go to the transfer section and search for the players you created. When you find them, they shouldn't have a small preview picture, they should have a blank profile picture. If so, congratulations, you can play forever. But if not, you need to go back to the beginning and do it again.
Important note: If you are going to create more players, first create 4-5 players quickly in a sloppy way and follow my instructions to the letter. If the profile photos of the sloppy players you created are empty, you can create the players you would create normally, this time you can create them carefully, which will save you time.
Thank you
M.G.