changing stylesheet for single posts in specific category

I’ve been searchign for week on the forum and still can’t figure it out.

i’ve been working on a gallery page for my friend. I was able to customize the CATEGORY PAGE by creating a category-7.php file. Thats not the problem, see here: https://www.sayuncleinc.com/?cat=7

However, i want to change the way the individual post looks when the post is in category 7. For example: https://www.sayuncleinc.com/?p=30

the problem is, if i change the page.php file, then all the other individual posts will change as well.

I can’t seem to figure out the conditional tags, and this did not work:

<?php if( is_page('') ) {
?>
<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<?php
}
if ( is_page() && !is_category('7') ) {
?>
<link rel="stylesheet" href="https://www.sayuncleinc.com/wp-content/themes/pride/style2.css" type="text/css" media="screen" />
<?php }
?>

so i have no clue what to do.. How can i use the conditional tags to change the style sheet when you are viewing a specific post from a specific category?