Hi

This support article should help:

https://support.mozilla.org/en-US/kb/about-config-editor-firefox

no that only helps me reset some not all at once

Do you just change a preference in respect of userChrome?

You might just need to reset:

toolkit.legacyUserProfileCustomizations.stylesheets

no i changed a lot but dont remmeber which

You can remove prefs.js in the Firefox profile folder with Firefox closed. If you have extensions installed then you may want to keep a copy of extensions.webextensions.uuids and restore this pref afterward as the UUIDs are used to link the extension to its storage (indexedDB).

You can use the button in "Help -> More Troubleshooting Information" (about:support) to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data