Indented menu items

I am building my own theme but I’m having problems with the navwalker menu. Is it possible to create a menu where indented menu items are constantly visible like the menu on this site:

https://www.kaitlin-howard.co.uk

Also I can’t seem to get each link to sit underneath each other. What am I missing?

https://www.kaitlin-howard.co.uk/wordpress/

Thanks!