Mobile menu not dependable

Sometimes when I check my site www.przemianaumyslu.pl on my android phone or my wife checks it on her Iphone the main menu does not open when I click on the button "MENU". Sometimes it works ok and sometimes it doesn't. Each time it doesn't I look up the website of my friend that also uses Catch Box Free Theme: www.jestescudem.com and the menu on her website always opens ok on my mobile phone. So it looks like it is an issue with the set up on of my theme. Could you please let me know what I can do to correct it? Best regards, Rafal