Help me! I killed my site with the about_us section

Hi!
I’ve got a big problem. I edited the about_us.php (sections/about_us.php) in the Zerif Lite template. I deleted the “OUR HAPPY CLIENTS” text and updated. After that my site lost (www.lindcom.hu) I tried to write it back, but it wasn’t the good solution ??
And now i tried do something in my wp admin and i got this message: Error establishing a database connection
This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at localhost. This could mean your host’s database server is down.

Are you sure you have the correct username and password?
Are you sure that you have typed the correct hostname?
Are you sure that the database server is running?
If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.

But before i deleted the text everything was all right. Hilfe :)) Big-big hilfe ??