How to remove "Designed by Themes & Co ·" in footer

You can change that info in class-footer-footer_main.php but i recommend you to do it in a child theme. The lines you are looking for are this ones

<div class="span4 credits">
    	<?php tc__f( 'tip' , __FUNCTION__ , __CLASS__, __FILE__ ); ?>
	    	<?php
		    	$credits =  sprintf( '<p> &middot; &copy; %1$s <a href="%2$s" title="%3$s" rel="bookmark">%3$s</a> &middot; Designed by %4$s &middot;</p>',
					    esc_attr( date( 'Y' ) ),
					    esc_url( home_url() ),
					    esc_attr(get_bloginfo()),
					    '<a href="'.TC_WEBSITE.'">Themes & Co</a>'
				);
				echo $credits;
			?>
		</div>

There you can edit that info and add your own by adding a link on the “href” and changing “Themes & Co” for your name.

You have copied php code—that should be in class-footer-footer_main.php in your child theme—into your CSS stylesheet (which shouldn’t contain php).

You should copy the class-footer-footer_main.php into the parts subdirectory in your child theme and delete all of the footer code you copied into your style css.