This type of quetion is better asked in the Nation specific part of the forum, in this case the KM section.

However every KM player should have a set of AA gunners, german AA is too usefull not to have access to.

General KM starters advice: make sure you have the crew to fill a BB6, 2 gunners, 2 AA-gunners, 1 scout and either 4 engineers and 4 repairers or 5 engineers and 3 repairers. Having BO's for both BB lines to level all of this up is a very good idea. Gunners should be higher level than BO's and having support that's very close to BO level or above is a big bonus as well.

Thank you very much and im sorry i made the message on the wrong board

Typically the only nations that should always have AA installed on their BBs are KM IJN and MN.
HOWEVER
Having AA to defend yourself from bombers and kill some scouts is nice even when playing nations with not so worthy AA (like USN).

Sniping at scouts and passing aircraft is best left to MN, IJN, and KM, in that order. But that doesn't mean other nations' AA is useless. US AA for example... A player who knows his angles can take US AA guns with 36 golden angles and clear the skies around him of circling fighters, which might allow him to launch a scout of his own. And the knockdown power against incoming bombers is impressive.

but like everything else, you have to practice. No nation is able to slap on AA guns and just start sweeping the skies.