Hi @mohannad ghawi ,welcome to Q&A forum!
Please try the following solutions:
In SharePoint designer 2013 Click on the File tab and then click on Account
In the Account page Click on “Switch Account” as highlighted below.
Type in the credentials of the site you are trying to open(Make sure it is the right account to access the SharePoint site) and restart your SPD.
If it does not work, try to clear the SPD cache and repeat the above steps.
If the issue still persists, I would suggest you uninstall and reinstall SPD and try again.
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