You also need modify the file index.php (line 21) and set like this:

Good afternoon, help please, configure the template, the search module ...

Please help! Layout Builder is not working in Joomla 3.7. I can't change the size of the new columns and add modules.

I'm delayed in replying to this...
Actually, that is not the only option for changing the font sizes. I took it upon myself to find the solution. Judging from the amount of questions that are neglected here - I couldn't rely on "support".
"you need to know more about code to custom the template" I know enough to read coding and alter them - which I was successful in doing without touching the custom.css file.
If you were unaware of an alternative other than just the custom.css method - you could have just said you didn't know.
Thanks anyways.

нужно либо в layout builder для мобильных устройств указать span 12, либо в custom.css по id блока написать новой свойство margin: 0 auto

Hey guys,
I setup website finish, if run on desktop very good, but run on mobile phone, not show slide and not run main icon so change module