Warning messages after updating to lagtest version of wordpress (4.5)

HELP! After updating to 4.5 these warnings came up and they appear at the top of every page of my site – globalspiritualstudies.com.

What are they and how can i get rid of them??

Warning: mysqli_real_connect(): The server requested authentication method unknown to the client [mysql_old_password] in /hermes/bosnaweb09a/b209/sl.globalss/public_html/wp-includes/wp-db.php on line 1489

Warning: mysqli_real_connect(): (HY000/2054): The server requested authentication method unknown to the client in /hermes/bosnaweb09a/b209/sl.globalss/public_html/wp-includes/wp-db.php on line 1489

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /hermes/bosnaweb09a/b209/sl.globalss/public_html/wp-includes/wp-db.php:1489) in /hermes/bosnaweb09a/b209/sl.globalss/public_html/wp-content/plugins/eshop/eshop.php on line 49