Hi I recommend you have a read of this [https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox article] that will explain how to delete your browsing history when you exit Firefox. Alternatively, you may want to use Private Browsing. You can read all about this [https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history here]. I hope this helps but if not, please come back here and we can look into a different solution for you.

You posted with a mobile device. Is your question about Firefox on a mobile device or on a desktop computer?