When the Thunderbird start page opens you cannot open the Account Settings with a click on the ≡ App-button in the upper right angle of the main window and select Account Settings?

It asks for a password and does not recognise the present one. I want to delete the account and reinstall it.

If you don't know the password, what would you expect to happen after deleting the account in Thunderbird and reinstall? A miracle? It would make more sense to me if you'd get in touch with your email provider and check with them about password reset options for your account.