Thanks to siggermannen and Dan Guzman I made it to the following query:

use [OmegaCA_Benchmark]

select 
a.database_specification_id,
a.audit_action_id, a.audit_action_name, 
a.class, a.class_desc, 
a.major_id,
object_schema_name = 
CASE 
    WHEN a.class_desc = 'OBJECT_OR_COLUMN' THEN OBJECT_SCHEMA_NAME(a.major_id)
    ELSE NULL
END,
object_name = 
CASE 
    WHEN a.class_desc = 'OBJECT_OR_COLUMN' THEN OBJECT_NAME(a.major_id)
    WHEN a.class_desc = 'SCHEMA' THEN SCHEMA_NAME(a.major_id)
    WHEN a.class_desc = 'DATABASE' THEN 'OmegaCA_Benchmark'
    ELSE NULL
END,
a.minor_id,
a.audited_principal_id, c.name as Principal_Name,
a.audited_result, 
a.is_group,
b.name as DB_Aud_Spec_Name, 
b.create_date, b.modify_date, 
b.audit_guid, 
b.is_state_enabled

from sys.database_audit_specification_details a

inner join sys.database_audit_specifications b
on a.database_specification_id = b.database_specification_id

inner join sys.database_principals c 
on a.audited_principal_id = c.principal_id

best regards
Altin