For changing the rewrite URL you need to know about the development. If you don’t have any coding experience then avoid this part. Here is a beautiful article to rewrite URL. check this and read it carefully.

• https://code.tutsplus.com/articles/the-rewrite-api-post-types-taxonomies–wp-25488
• https://wordpress.org/support/topic/taxonomy-rewrite-same-as-custom-post-type-slug/

Or you can do it with some plugin like – https://wordpress.org/plugins/wp-better-permalinks/

Also if you don’t want to go with this then here is another tips for you. For apply this thing you need to install materia-child theme then you can added this code into materia-child function.php

    /*
    CHANGE SLUGS OF CUSTOM POST TYPES
    */
    function change_post_types_slug( $args, $post_type ) {
       /*item post type slug*/   
       if ( 'portfolio' === $post_type ) {
          $args['rewrite']['slug'] = 'projects'; //Your URLs
       }

       return $args;
    }
    add_filter( 'register_post_type_args', 'change_post_types_slug', 10, 2 );

    /*
    CHANGE SLUGS OF TAXONOMIES, slugs used for archive pages
    */
    function change_taxonomies_slug( $args, $taxonomy ) {

       /*item category*/
       if ( 'portfolio-category' === $taxonomy ) {
          $args['rewrite']['slug'] = 'locations'; //Your Ctegory URLs
       }

       return $args;
    }
    add_filter( 'register_taxonomy_args', 'change_taxonomies_slug', 10, 2 );