I tested a little bit longer and noticed the following:
1. when you click menu on mobile, you select for example “O Psychoterapii” then the web site is going to the target site but, the menu is still open. can this close automatically after the selection? Please note that I have sub-menus as well.
2. When I go to “Uslugi” then and select any subpage – this is shown without the main title of that sub-page. – it looks like a logo with wider top menu section overlapping the top section with the title of the subpage . On big screens it is showed properly, but on mobile, not really