German DD use HE 1/6 pen rule if i remember correct and German AP only good at damage. it has bad ricochet angle and at long range you mostly get ricochet, can only use when enemy showing full broadside.
I recommended to watch this channel. https://www.youtube.com/user/farazelleth/videos
He made guide for CV both IJN and USN.
You can spend some time to watch them and learn to improve yourself.