Unfortunately when this happens no users on here can help since you lost the password. And what also what is Master password here?

Unfortunately, you will have to reset your password which will mean losing saved logins. I suggest that you backup your profile. The files you particularly want are logins.json, logins-backup.json and key4.db. https://support.mozilla.org/en-US/kb/reset-your-primary-password-if-youve-forgotten-it https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_what-information-is-stored-in-my-profile https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile