Try:
SELECT * FROM tblAuftragMulti
WHERE OrderId = '305' AND
Status != 'true' AND
Status != 'false'
But you shouldn't be storing data like that: you are repeating strings a lot and that leads to errors when someone adds a row with "TRUE" or "False" and it fails to match your criteria. You'd probably be better off a separate table containing the text strings, and a foreign key to the ID; then use a JOIN to get the text back if you need it.