Why does the /product-category/ link refer to the single.php file?

Question

WordPress

Hello !
I'm trying to display products from a certain category and this kind of link /product-category/ links to the single.php file and no other file, although it should link to taxonomy-product_cat.php, I don't know how to fix it.
And another question about image compression. It is necessary that WordPress does not compress images.
I installed the Tiny PNG plugin, checked the box to load images without compression, and added this hook

add_filter( 'jpeg_quality', function ( $quality ) {  
  return 100;
} );

Both options did not help (
Help me solve these problems, I will be very grateful)