Update problem

Hi , my current version is 3.0.8 and I want to update to 3.0.9. I uploaded "install" dir from the update package. When I'm going to update (by clicking "Now start the update process by pointing your browser to the install folder.") , I'm getting this error and the update can't start :

[phpBB Debug] PHP Notice: in file /includes/constants.php on line 294: Constant ANNOUNCEMENTS_CENTRE_TABLE already defined
[phpBB Debug] PHP Notice: in file /includes/constants.php on line 295: Constant GROUPS_ONLY already defined
[phpBB Debug] PHP Notice: in file /includes/constants.php on line 296: Constant EVERYONE already defined
[phpBB Debug] PHP Notice: in file /includes/constants.php on line 297: Constant GUESTS_ONLY already defined
[phpBB Debug] PHP Notice: in file /install/index.php on line 361: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706)
[phpBB Debug] PHP Notice: in file /install/index.php on line 362: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706)
[phpBB Debug] PHP Notice: in file /install/index.php on line 363: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706)
[phpBB Debug] PHP Notice: in file /install/index.php on line 364: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706)