Thanks for reaching out, Muhammed. Can you confirm if the old device still appears under account.microsoft.com/devices after you selected Remove device?
If it does, sign in to that page, select the device, and choose Remove this device again. This removes it from your account but does not affect your Windows 11 license. To use the license on a new computer, check if it is a retail license (which can be transferred) or an OEM license (tied to the old device) by running slmgr /dli in Command Prompt. If it is retail, sign in on your new PC with the same Microsoft account and use Settings > System > Activation > Troubleshoot to activate Windows.