Mobile menu problem – link handling touchstart instead of touchend

Hello, I have an navigation menu problem. When pressing on a smartphone (ioS, Safari)the navigation icon in the top left corner of clicks.bissantz.de then the mobile menu is getting in immediately while pressing. The problem is that as soon as you release the finger from that icon the new link from the navigation menu that has driven in to the same place where your finger is called. I just want the nav menu open on touchend (mouseup) not on touchstart. I wonder why the site partner.bissantz.de with the same theme and css is working correctly. Do you have an advice? Thenk you in advance. Kind regards Olaf