First, please update to Firefox 63 or later. Firefox 59 is very out of date.

Then, can you give an example website where you see this happening?

Hi Tzircon, there are two common reasons that Firefox will go to HTTPS even if you type HTTP:

(1) "Strict Transport Security"

This is an instruction from a website to always use HTTPS.

(2) Add-ons like HTTPS Everywhere

These add-ons try to upgrade your connection to HTTPS at every opportunity.

Is HTTPS creating a problem for you on some site?