The British public elects the MEPs in a democratic election! That is how Farrage got to Brussels in the first place. I can link you to the relevant pages if you don't believe it!
The European Council which selects the EU president consists of all democratically elected heads of state. Last time I checked, the British public still does elect their PM. Or maybe not?

......Please, outline here for everyone how you "elected" Boris Johnson as your PM? Hmmmm, I am pretty sure it wasn't the British public.
As for your second assumption - the emphasis on Juncker's statement is on:
"Boris Johnson and myself don’t think it’s possible to give another prolongation." There you go, I even highlighted it for you, so you don't have to remove your EU-hate goggles to read properly.