Fatal error when accessing page

Hello Support,
when I try to access my hompage http://www.motionnet-systems.de I receive a blank screen saying: Access denied.
When I try to log into http://www.motionnet-systems.de/wp-admin I reveive a fatal error:
Fatal error: require_once(): Failed opening required ‘/homepages/43/d122581636/htdocs/wp-load.php’ (include_path=’.:/usr/lib/php5.4′) in /homepages/43/d122581636/htdocs/wp-admin/admin.php on line 31

My wordpress account (motionnet) is not valid any more (can’t log in): message “no such account”

Wordpress version is not known, but it is pretty old (no updates performed over 2-3years).

My questions:
– whow can I reactivate my account “motionnet” again?
– how can I repair my page: http://www.motionnet-systems.de? Back-up is available.
– or is it better to set it up from scratch?

Thanks for help.

Best Regards

Sigi Krist