Customizing does not work

Hello,

in Hemingway theme I am now unable to customize my site. The function worked few weeks ago, now it is not possible to do any changes in it.

It might be that I erased some time ago some part of an original code, I’m not sure. If this is the case, where customize.php is hidden and how can I get the original piece of code..?
If the problem is somewhere else, what should that be?

Thank you,
Antonin, site antoninbrinda.com (but not active at the moment)