This is easier to be done with CSS. Something like this could do the job. Add this to your child theme’s style.css or under Customizer > Additional CSS.
I checked the page, indeed it’s not working, we need to have a look at the WordPres debug.log file to see if any further info is available there.
We’ll need access to your site to check this, so please send us an email at support@pokatheme.com with your website FTP credentials to see what’s wrong.
When you are using a child theme (PokaTheme child), then all the functionality of the parent theme (PokaTheme) still remains, this is the purpose of the child themes.
So you should activate the PokaTheme child theme on your website.