How to disable Firefox's search (Ctrl + F keyboard shortcut) to be used for the website's internal search?

In numerous cases i have found not to be beneficial when website's search function is activated on Ctrl+F keyboard shortcut and where is better to use regular Firefox on-page search instead. I think that the good site has search button/area visible so i can use it when needed.

So please how to disable Firefox's search (Ctrl + F keyboard shortcut) to activate website's internal search? I want to always use regular Firefox on-page search that i now trigger by left Alt (to show the FF menu), click Edit menu, click Find in page.... (since Ctrl+F is occupied by website's internal search).