sometime it say firefox wont work unless its restarted

Hello, First, to make sure your tabs don't disappear when doing this go to settings > general, then go to the startup section, then check the box for "Open previous windows and tabs". If enabled, skip this step. If not, then you can disable it after you are done. Then, you can try going to Task manager (Ctrl + Shift + Esc), then end task for any instances of Firefox.exe. Next, to prevent this in the future, go to Settings > general, then scroll down to the Firefox updates section, then check the option for "check for updates but let you choose to install them"