Maybe I find some problem but probably it is problem in code look at the pictures please
if you do something wrong in contact form tab is just around the message that something is wrong but if the email is sended normaly than message that says it is sended have green round box around the whole contact form (sorry for explanation)
Thanks for pointing out the contact issue and also the code that you used.
To have the CSS styling permanent I would recommend you to use a custom CSS plugin to handle it.
This way you can replace the theme files without worrying about erasing your CSS, but you should always keep a local backup of the files, regardless.
The best practice would be to set up a child theme if you will do any file modifications, but as far as CSS styling a plugin is all you need.