this person does not speak English and does not answer my questions. Fred

Open the history sidebar (Ctrl+H), search for the site, right-click and choose "Forget about this site".

It is not about a website, but about autofilling on any site. how do I change/edit/delete some of the autofill entries stored by Firefox? Fred

You can use these steps to remove saved items from an autocomplete drop-down list.

1. click the (empty) input field on the webpage to open the drop-down list
2. highlight an entry in the drop-down list with cursor Down key
   do not click the mouse or press the Enter key
3. press "Delete" or "Shift+Delete" to delete the highlighted entry

Note that hovering with the mouse doesn't work.

• https://support.mozilla.org/en-US/kb/remove-websites-address-bar-suggestions
• https://support.mozilla.org/en-US/kb/firefox-suggest