Database connection details is 100% correct! And he gives me this ERROR:
Warning: Cannot modify header information - headers already sent by (output started at /home/webdocs/domains/.../wp-admin/setup-config.php:22) in /home/webdocs/domains/.../wp-includes/wp-db.php on line 308
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 mysql69.zdravljetrade.co.yu. This could mean your host's database server is down.
I was try manual install, but doesn't help either.