Unable to edit or remove “returning customer login reminder” on “Checkout” page

i’m just really frustrated cause unable to edit or remove “returning customer login reminder” on the “Checkout” page …

the there written message is: “Storefront theme Returning customers login. New users register for next time so you can:” – and seems that not complete.
but didn’t found it to edit, to translate, not in any language files, nore in wc, wc germanized or in storefront templates …for editing. so i’m very interested where this fault is located – seems to be a function, but where?! (or does it’s a php, a template, what?)

now i can’t get my new built store online with such ’n ugly disfunction.
need your help to find out where and how to edit this!
thanks in advance!

system: woocommerce, germanized / storefront / all last versions (& child theme)