Hi Jan Kovač,
Regarding your issue, it could be the cache issue. Can you try below steps:
1. Clear your web browser cache.
2. Clear your Joomla cache if you've enabled Joomla cache.
3. Go to EasySocial backend under Themes -> Compiler and under Site Themes section, select the theme that you currently used in your EasySocial, e.g. Wireframe and click 'build' button on the right to rebuild the styling for your EasySocial.
Let me know if the above work for you or not. If problem persist, can you edit your thread and provide us your Joomla backend admin access under 'site details' section so that we can investigate your issue further.