After deleting the webapp it will be available to restore for 30 days. I believe that you will have to wait that period to retry that name. If you don't want to wait, you can choose a different name for your webapp.
How do I restore a deleted web app or a deleted App Service Plan?
You can also try raising a ticket to assist:
----------------------------------------
If this is helpful please accept answer.
@Maheboob Patel It's not clear what you are attempting to do based on your screenshot. If I were to guess though, that screenshot looks like you are attempting to use Azure Cloud Shell directly in the Azure portal. Cloud Shell requires a storage account.
A way to get around that would be to use Azure CLI directly from your local machine. See here for more information.