Multiple [gallery] with different styles : [gallery1], [gallery2]…

I’d like to create 2 gallery shortcodes on my wp-site – [gallery1] and [gallery2] with 2 different corresponding styles (in my style.css); and use it in default way – by inserting a [gallery] into post, but having a choice between 2 different prestyled galleries – [gallery1] and [gallery2] (1 for squared thumbnails / 2 for panoramic ones – both with different frames).
I’ve already managed to customize the native [gallery] to my needs: gallery_shortcode in ‘media.php’ + style in ‘style.css’ (see test-post).

How can customize the native wordpress [gallery] and have 2 styles ([gallery1] [gallery2] shortcodes) instead of one?

I’ve tried (in media.php) to copy the default gallery shortcode ( add_shortcode('gallery', 'gallery_shortcode'); .......... return $output;}), inserted it after the default one and changed everywhere in the code ‘gallery’ onto ‘gallery1’ and ‘gallery2’ respectively:
(add_shortcode('gallery1', 'gallery1_shortcode'); ... and add_shortcode('gallery2', 'gallery2_shortcode'); ...)

I’ve tried and inserted [gallery1] and [gallery2] into a post one after another but it didn’t work well – the images were framed and resized as writted in style.css, but it seemed that both galleries were inserted twice and one overlayed the other one.

I’m not an advanced wp-user, nor a designer or coder. I understand some parts of the code and know how to style the css parts, but media.php is a complete mess for me ?? Could anyone, please, help me with this code, cause I’m definitely doing something wrong ??

Thanks in advance! Greya