<?php
/*
Template Name: Skils

*/
get_header();
?>

	<section id="primary" class="content-area">
		<main id="main" class="site-main">

			<?php
/*Page loop*/
			/* Start the Loop */
			while ( have_posts() ) :
				the_post();

				get_template_part( 'template-parts/content/content', 'page' );

				// If comments are open or we have at least one comment, load up the comment template.
				if ( comments_open() || get_comments_number() ) {
					comments_template();
				}

			endwhile; // End of the loop.
/*End page loop*/

/*Post loop*/			
			     // Define custom query parameters
                    $custom_query_args = array('category_name' => 'how_to', 'posts_per_page' => 2);
					
                 // Instantiate custom query
                 $custom_query = new WP_Query( $custom_query_args );

                 // Pagination fix
                 $temp_query = $wp_query;
                 $wp_query   = NULL;
                 $wp_query   = $custom_query;
				 
//print_r($custom_query);

                 // Output custom query loop
                if ( $custom_query->have_posts() ) :
                     while ( $custom_query->have_posts() ) :
                        $custom_query->the_post();
                        // Loop output goes here
		                get_template_part( 'template-parts/content/content' );
                     endwhile;
	

                endif;

            // Reset postdata
            wp_reset_postdata();

			// Previous/next page navigation.
			twentynineteen_the_posts_navigation();
			
             // Reset main query object
             $wp_query = NULL;
             $wp_query = $temp_query;
			 
/*End post loop*/

			?>

		</main><!-- #main -->
	</section><!-- #primary -->	
<?php
get_footer();

I used the print_r to see the content of the $custom_query and the correct number of pages is shown but the content of only the first two posts is shown. If I change the page number to -1 all the page content is shown.

Thanks

Mark

(please note: I’ve commented at the lines I’ve added for you)

<?php
/*
Template Name: Skils

*/
get_header();
?>

	<section id="primary" class="content-area">
		<main id="main" class="site-main">

			<?php
/*Page loop*/
			/* Start the Loop */
			while ( have_posts() ) :
				the_post();

				get_template_part( 'template-parts/content/content', 'page' );

				// If comments are open or we have at least one comment, load up the comment template.
				if ( comments_open() || get_comments_number() ) {
					comments_template();
				}

			endwhile; // End of the loop.
/*End page loop*/

/*Post loop*/			
			     // Define custom query parameters
				 
					/* THE BELOW LINE IS A NEW ADDITION */
					$paged = ( get_query_var( 'paged' ) ) ? get_query_var( 'paged' ) : 1;
					
                    $custom_query_args = array(
						'category_name' => 'how_to', 
						'posts_per_page' => 2,
					/* THE BELOW LINE IS A NEW ADDITION */
						'paged' => $paged
					);
					
                 // Instantiate custom query
                 $custom_query = new WP_Query( $custom_query_args );

                 // Pagination fix
                 $temp_query = $wp_query;
                 $wp_query   = NULL;
                 $wp_query   = $custom_query;
				 
//print_r($custom_query);

                 // Output custom query loop
                if ( $custom_query->have_posts() ) :
                     while ( $custom_query->have_posts() ) :
                        $custom_query->the_post();
                        // Loop output goes here
		                get_template_part( 'template-parts/content/content' );
                     endwhile;
	

                endif;

            // Reset postdata
            wp_reset_postdata();

			// Previous/next page navigation.
			twentynineteen_the_posts_navigation();
			
             // Reset main query object
             $wp_query = NULL;
             $wp_query = $temp_query;
			 
/*End post loop*/

			?>

		</main><!-- #main -->
	</section><!-- #primary -->	
<?php
get_footer();