How to merge all my pages into one, while keeping a menu bar?

I have currently a website with a basic organisation : 5 different pages (“About us”, “projects” …etc.) with a typical menu bar.

I would now like to have all the pages into a single one.
1) How can I bring all my pages into the home page?

I would also like to keep a (sort of) menu bar: for instance, clicking on “projects” in the menu bar will bring the reader on the project part of the main page.
2) How can I build such a menu bar?

I have (unfortunately!) limited knowledge of WordPress & coding. Detailed answers would be very much appreciated 🙂

Thanks,
Inès