Design Wordpress page and menus for online course

Hi.

I need to design a web page for an online course.

The web is in Wordpress and has the Enfold theme installed, which is very versatile.

You only need to make a single template page. It is not required to do the whole web, only the template page.

The design must be as similar as possible to the attached image:

- Side menu that shows by default only the mother pages (pages), the children (subpages) will be seen only when clicking.

- The side menu will be fixed, it will not scroll when scrolling on the screen. Only the content will scroll. If the menu options are too many to appear with the fixed menu, the menu will scroll, but independent of the content section.
As seen in the attached image.

- Although it is not necessary for the design to be exactly like the image, it must be clear and clean. I have tried with Wordpress menu plugins and they are not clear and with good design.

- It must be responsive, and the menu must work on tablets and mobiles

Thank you.