have problem with my site on firefox browser

I have a problemwith my firefox browser and my site, all time i will open the site in firefox than have i this bug on site .
Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 571

Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 550

Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 550

but other people see it not. i have make clear all cache from browser than is ok.
next time will open my site in browser is the them bug. all time on my pc or firefox.
when i will go in admin when the first bug i see on site then can not go in admin
then see i this bug infos
Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart.php on line 1275

Warning: array_sum() expects parameter 1 to be array, null given in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 348

Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 571

Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 550

Warning: Invalid argument supplied for foreach() in /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart-totals.php on line 550

Warning: Cannot modify header information – headers already sent by (output started at /www/htdocs/w015b01b/notfall-id.de/wp-content/plugins/woocommerce/includes/class-wc-cart.php:1275) in /www/htdocs/w015b01b/notfall-id.de/wp-includes/pluggable.php on line 1210

can someone me help what is it for problem.
all other people can not see the bugs and in other browser is it not
best greeting micha

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