Changes in Child Theme are not inherited

Hi, I wanted to changes some things in the navigation bar of BP corporate. So I did as recommended: I copied navigation.php from BP corporate to Bp corporate child and adjusted the things I wanted. But the changes didn´t show...tried to delete navigation.php in BP corporate, but got an error message (of course :wink: ). The changes in navigation.php DID work when I copied it to the original BP corporate theme (NOT the Child theme). Why doesn´t it work when I change the child theme?