You need to do some basic research on things like ‘Backing Up’, there are many approaches and solutions out there, from VaultPress service, to backup plugins, to your webhost provided services or cpanel/plesk type site/user account backups.
The same advice applies for deactivating plugins when you can’t access the admin, rename the plugin directories. That media plugin must have downloaded and installed otherwise it wouldn’t have thrown the error. Deactivate all plugins, update WP and establish that works as expected then re-activate or download a new copy of BP, as you’re so far behind in BP versions you will need to perform stepped upgrades to get to the latest stable version. Check the BP Codex for advice on this aspect.
