Well you can try the following:

1. Restart the computer.
2. Switch to Wi-Fi, if possible. 
3. Force Windows to reinstall the Ethernet driver.
4. Run the built-in network troubleshooter, located here: Settings > System > Troubleshoot > Other troubleshooters.
5. Reset the Windows 11 network settings

Hi, i am tried all steps but its not working. İ'll download windows 11 lan driver from dell site but nothing happened. i think i will go back to windows 10. 

Well yes you can roll back to windows 10. But you can also try to reinstall the windows 11 in your system.