Unity required Api level 23 Please help!!!,Unity Requested Android Api 23

I have Unity 2017.1.2p3 and i trying to build a project
but when I build the game I get this error:
“required Api level 23.”
I already have the android sdk 6.0 API level 23 installed and re-installed
and i have the last version of sdk manager and i changed my api platform name to android_23 and i run sdk manager and unity as administrator.
but i still get this error.
when i click on update:
and when i click on use highest :
“the latest installed sdk on the system is 0”

what can i do to fix this?

I got this error when I used only the “tools” directory of SDK. The build went further when I used the full install of Android Studio. Anyway, it fails a little later as explained in this post: https://answers.unity.com/questions/1344311/unity-android-sdk-error.html
I tried the described fixing without success…