How best to change the main menu to all vertical?

Hi,

I am slowly working out what WordPress is all about and at this point I want to try to keep everything as simple as possible.

The problem I have now is that I’m aiming to make the main menu appear verticallly from the hamburger sign, even in wide screen devices.

Twenty Nineteen is obviously putting the first menu items into a row until it runs out of space.

The purpose of making it all vertical is related to the menu items all being just anchors within this one page, so the menu item list gives the overview of topic.

At the end I will put the usual About page, but mostly I’m using only links to anchors on this one page.

I’ve tried the Responsive Menu plugin but the freebie version is too limited.

I’ve put a child theme in place to do some CSS work on Twenty Nineteen, but looking at what it’s got already, it looks like a hard way of doing it!

Any suggestions?

The site is very much a playground still!

Thanks ??

The page I need help with: [log in to see the link]