I create new file archive-(custom_post_name).php, and I tried to copy inside the code from index.php.
It works without styling, but works.
Now I have trouble to activate featured image in post editor. I did some research and found that I have to put to my function.php this code:
add_theme_support( 'post-thumbnails', array( 'post','custom_post_name' ) );
But this not work for me 🙁
Any idea how to activate featured images?