Cool, do all your settings in google search a item, then book mark that page or, while you exit firefox, goto file and do exit, it asks for save and quit, do that...

Thank you

Which version of Firefox are you using?

Such settings are stored in a cookie that you must allow: Tools > Options > Privacy > Cookies: "Exceptions"
Make sure that you do not use Neueste Chronik löschen to clear the Cookies and the 'Site Preferences'.

Also check that you do not start Firefox in Private Browsing mode (Tools > Stop Private Browsing is grayed)
Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
Un-check: [ ] "Automatically start Firefox in a private browsing session"
You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"

Cool, This is another way to reset your firefox to factory setting so try it may solve your problem " go to address bar type about:config it will ask of confirmation press to continue, here you can see list of preferences, some of them are in bold letters so those bold entries are user preferences , right those and select reset... and restart your firefox.. try now my to exit via file >exit it should ask you for "save and exit".."

Thank you