You can also check Tools > Options > Privacy > History: "Remember search and form history"

Did you ever use Delete browsing, search and download history on Firefox to clear personal data?

• Make sure that you not run Firefox in Private Browsing - Use Firefox without saving history mode
• In Private Browsing mode some menu items are disabled (grayed) and features like visited links are disabled and not showing
• You are in Private Browsing mode if you see "Tools > Stop Private Browsing", possibly grayed

• You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"
• To see all History settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Uncheck: [ ] "Automatically start Firefox in a private browsing session"

Facebook is the only website that won't save my e-mails that i've typed in

Do you mean user name and passwords or saved form data ?

Did you check the exceptions: Tools > Options > Security: Passwords: Exceptions ?

• Password manager - Remember, delete and change saved passwords in Firefox
• http://kb.mozillazine.org/Password_Manager

• Websites remembering you and automatically log you in is stored in a cookie.
• You need an allow cookie exception (Tools > Options > Privacy > Cookies: Exceptions) to keep that cookie, especially for secure websites and if you let cookies expire when Firefox closes
• Make sure that you do not use Delete browsing, search and download history on Firefox to clear the "Cookies" and the "Site Preferences"

• Enhanced Tracking Protection in Firefox for desktop