Website Using Up Server Resources - Many Error Messages

At the moment there seems to be quite a major problem with a site we have at www.vamoz.be.....at times it refuses to load, and it´s impossible to make changes in the backend. So there seems to be something eating up server resources.

These are the errors in the log:

[2016-03-09 11:59:53] (ERROR @ /index.php) `blog_link` is not a valid integer and may not be passed to makeUrl()
[2016-03-09 11:56:52] (ERROR @ /index.php) [pThumb] Resource: 72 || Image: (none)
File not found: /home/sites/vamoz.be/public_html/[[+pdf-link]] *** Skipping ***
[2016-02-14 14:24:40] (ERROR in xPDOConnection::connect @ /home/sites/vamoz.be/public_html/core/xpdo/xpdo.class.php : 3043) SQLSTATE[HY000] [2006] MySQL server has gone away
[2016-02-14 14:24:40] (ERROR @ /index.php) Error preparing statement for query: SELECT `modSession`.`id` AS `modSession_id`, `modSession`.`access` AS `modSession_access`, `modSession`.`data` AS `modSession_data` FROM `v4m0_session` AS `modSession` WHERE `modSession`.`id` = ? -


Any help from you guys would be greatly appreciated!

Part of that looks like a MySQL overload, what kind of server is this on?

Also might want to check the database for corrupted tables, particularly the session table.