[SOLVED] Problem after automatic upgrade from oc 7 to oc 8

Hi all, I have an owncloud 7.x installation.
A colleague of mine accidentally run the upgrade proposed from owncloud and right now, the webpage doesn't respond

wget cloud.domain.com
--2016-11-16 11:51:42--  http://cloud.domain.com/
Risoluzione di cloud.domain.com (cloud.domain.com)... 37.159.170.102
Connessione a cloud.domain.com (cloud.domain.com)|37.159.170.102|:80... connesso.
Richiesta HTTP inviata, in attesa di risposta... 500 Internal Server Error
2016-11-16 11:51:44 ERRORE 500: Internal Server Error.

Owncloud was installed from tar.gz on a debian 7
apache 2.2.22
php 5.4
5.5.46

Right now this should be my owncloud version
sudo -u www-data php occ -V ownCloud version
ownCloud version 8.0.14

This are the errors I find in apache2/error.log
[Tue Nov 15 15:39:34 2016] [error] [client 192.168.1.102] script '/mnt/owncloud_data/cloud.domain.com/gocs/v2.php' not found or unable to stat
[Tue Nov 15 15:40:11 2016] [error] [client 192.168.1.102] script '/mnt/owncloud_data/cloud.domain.comg/ocs/v2.php' not found or unable to stat
[Tue Nov 15 15:40:35 2016] [error] [client 192.168.1.132] script '/mnt/owncloud_data/cloud.domain.comg/ocs/v2.php' not found or unable to stat
[Tue Nov 15 15:41:34 2016] [error] [client 87.4.184.43] PHP Fatal error: Class OCA\Contacts\Share\Addressbook contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (OCP\Share_Backend::isShareTypeAllowed) in /mnt/owncloud_data/cloud.domain.comg/apps/contacts/lib/share/addressbook.php on line 130
[Tue Nov 15 15:41:39 2016] [error] [client 192.168.1.132] PHP Fatal error: Class OCA\Contacts\Share\Addressbook contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (OCP\Share_Backend::isShareTypeAllowed) in /mnt/owncloud_data/cloud.domain.comg/apps/contacts/lib/share/addressbook.php on line 130
[Tue Nov 15 15:41:43 2016] [error] [client 192.168.1.132] PHP Fatal error: Class OCA\Contacts\Share\Addressbook contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (OCP\Share_Backend::isShareTypeAllowed) in /mnt/owncloud_data/cloud.domain.comg/apps/contacts/lib/share/addressbook.php on line 130
[Tue Nov 15 15:41:44 2016] [error] [client 192.168.1.132] script '/mnt/owncloud_data/cloud.domain.comg/ocs/v2.php' not found or unable to stat
[Tue Nov 15 15:41:45 2016] [error] [client 192.168.1.132] PHP Fatal error: Class OCA\Contacts\Share\Addressbook contains 1 abstract method and must

Do you think it worth to try to fix it or is it better to restore from the backup?
Shall I run 'sudo -u www-data php occ upgrade' from command line or am I going to mess-up things even more?

Thank you.

You can upgrade to OC 8.0, if you have a backup there should be no problem to proceed. Please disable the calendar and contact apps (or just delete the folders from the apps/ directory, https://github.com/owncloud/core/issues/14852). Then it should upgrade properly.

OC 8.0 has also reached EOL, so you should upgrade further to at least OC 8.1. Keep in mind that you cannot skip major upgrades, so you have to do 7.0->8.0->8.1->8.2->9.0->9.1

Once removed the calendar and contact apps it works!
Thank you very much!