Template files override

Hi folks,

I’m a newbee atwordpress and try to create a child theme. Now I struggle with file overrides. I want to edit the file

/themexy/includes/widgets/my-requestquote-widget.php

So I copied it into my Childtheme Folder and created there the same file structure…

/childtheme/includes/widgets/my-requestquote-widget.php

and editet the stuff that i wanted to change (adding some new icons). The thing is, that the file is obviously not loaded by wp. So I tried to add this line into the functions.php file, which I created within the child theme folder.

require_once( get_stylesheet_directory(). ‘/includes/widgets/my-requestquote-widget.php’ );

But now I get the following error:
Cannot redeclare class MY_RequestQuoteWidget in….

I guess it is a pretty stupid question but you would be a great help if you could give me any clues.

cheers
dan