Hi there,
Welcome to SeaTheme forum.

Please use tag <br> for line breaks. like:

Tsdfas asfasf asdfasf<br>
tag1, tag2

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook

Hi,

I suggest you use Media library as source for the masrony grid. In WordPress, the the excerpt function by default removes HTML tags, including br tags.

If you still wish to use Portfolio, I can only offer you an alternative solution:
please go to Plugins>Plugin editor, edit the BM Content builder: /include/templates/modules/module-masonry-grid.php, line 1065,
update as:

    $excerpt = get_the_excerpt( $loop_post_id );
    $excerpt = wpautop( $excerpt );  
    $html .= '<div class="grid-item-des">' . $excerpt . '</div>';

This code change will implement line breaks by default, so you do not need to add br codes in the excerpt.

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook