Hello Vojtěch Z.,

You can make a copy of the project where you use one of the mobile templates available in the program and where you set a bigger font size. Try to add also more space between the menu buttons in step 1 - main menu stile. Once done you can upload the mobile version project in a subfolder and then use as example in the main project the welcome page with the link to the desktop and mobile version of the site.

Google explains how to set everything correctly here: https://developers.google.com/webmasters/mobile-sites/mobile-seo/configurations/separate-urls

Many thanks!