Showing content from WordPress ruins page CSS using WP_Query, without, content does not show

Your’s css is messed up becouse you have invalid html code.

I’v counted 9 opening <div> tags and only 8 ( 7 in seccond code block ) closing tags

Fix the html and your css will work just fine.

About the_content() in your example it should work just fine, check if you have content added to post.

When you’r using the_excerpt() check if your excerpt field ( or more button in content field ) is added.

Also try to fix closing <div> tags, becouse of them you may not see all the content ( may be that’s the problem )