The data is stored locally changing password will not delete them from the computer they were stored on. Once you delete folder and if that contained the data it's gone. You can't change your password if you forgot the password. Reset requires the login email account to get the reset password change. That login and Firefox account login are two different logins. No one here can fix your lost password as that isn't something users on here can help with.

thats not what I'm asking. all my information is synchronized with mozilla sync right? if so, it should have history passwords etc. If I try to reset my password (because I forgot it) all this information will be erased as you say. So I want to know if I can avoid this and change my password without losing my mozilla sync data.

Resetting the password for the Firefox Account because you do not remember the password will remove all data stored on the Sync server because this password is used to encrypt your data locally for security reasons before it is uploaded to the Sync server and only this password or a possible recovery key can decrypt this data.

• https://support.mozilla.org/en-US/kb/reset-your-firefox-account-password-recovery-keys

There is nothing in the recycle bin and also no system restore point that you can use ?

You can look a utility to browse System Restore points.

• https://www.shadowexplorer.com/
• https://www.nirsoft.net/utils/shadow_copy_view.html