I want to design a background with a very high (steep) edge to the right (see image). Moreover, I have only managed to create a stright line slope so far.

 

https://i.imgur.com/ghRW2k4.png

This can be done by using an SVG as a background image.

Thank-you for the reply. I'm just searching youtube videos now for help

Not sure you need a YT video for this?  If doing something like this is a problem then I suggest you do some study around CSS fundamentals along with some reading around SVGs.

14 hours ago, squeezeeur said:

I'm just searching youtube videos now for help

Why YT?

Search Google for SVG shape generator and someone has already done all the hard word for you.

quick job with the pen tool and then export to svg