I tried disabling the W3 Total Cache plugin again and it seems like it was not the problem cause the cart is still showing wrong item numbers. Its on different pages than before also.
I got it working once when i put pages in the w3 “never cache these pages”, but when i deleted the item from shopping cart some pages showed that it was still there.
Anyone that knows what i can do to get the customers cart to clear itself after x amount of time and show the correct item numbers on every page? Or is there any other similar plugin?