[Dragokas]

It is intended to work with external MySQL database only.
If 127.0.0.1 not work for you, try to set server's public IP there.
I'm not completely sure. Still learning sm database stuff. This is my first experience.

Also, are you sure "database" "l4d2_stats" schema is exist on your server?
If you don't know what is it, it's better to read some manuals. I don't think this topic is appropriate place for such discussion. It's better you open separate thread in General forum and leave here a link.