Functions.php is giving grief

Hello,

I work with theme Twenty Fourteen. It works, but as soon as I want to change something in functions.php, this is where trouble starts. When I copy the exact php file to my child theme, the site crashes. This makes no sense to me, because obviously left in twenty fourteen theme itself, it works just fine. But I cannot get a functions.php in my child theme without either the site crashing, or if I use a clean php and just add a few codes, these codes to appear on the site (readable, not implemented).

Does anybody know what I am doing wrong?