In the file shapely/inc/widgets/widget-home-parallax.php replace this line : <p><label for="<?php echo $this->get_field_id('button2_link'); ?>"><?php esc_html_e('Button 1 Link ','shapely') ?></label>
By that one : <p><label for="<?php echo $this->get_field_id('button2_link'); ?>"><?php esc_html_e('Button 2 Link ','shapely') ?></label>
2/ About the button not showing or being white with a white text in a white sea
In the same file replace this line : echo ( $button2 != '' && $button2_link != '' ) ? '<a class="btn btn-lg btn-white" href="'.$button2_link.'">'.$button2.'</a>': '';
by that one : echo ( $button2 != '' && $button2_link != '' ) ? '<a href="'.$button2_link.'">'.$button2.'</a>': '';
If you make changes in the theme file then you have to make these changes again after theme updation as changes made in the theme files get lost on theme updation.