Getting Un Wanted Gallery Shortcode In The Page on Loop

All filters applied to the 'the_content' hook (including shortcode rendering) are not applied when you call get_the_content().

This is why you get raw shortcode from your content.

You could use the_content() instead, or use apply_filters directly in your template.

In other words, replace this line:

echo '<p class="p-paragraph" style="text-align:left">'. get_the_content().'</p>'; 

with either (preferred method):

echo '<p class="p-paragraph" style="text-align:left">';
the_content();
echo '</p>'; 

or alternatively:

echo '<p class="p-paragraph" style="text-align:left">' . apply_filters( 'the_content', get_the_content() ) . '</p>'; 

To learn more about these functions, you may look at the documentation and source code at the_content(), get_the_content() and 'the_content' hook