Why is it so hard to show the URL of the current category and how to do it?

On a category archive, get_queried_object_id() will give you the category’s ID, which you can pass to get_category_link():

echo get_category_link( get_queried_object_id() );

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)