So @Gnom1 @Wicki @Darktrooper nun seid ihr alle im richtigen Bereich und Thread!
If you come from Lollipop (from 1 to 16), if you come from Marshmallow (from 1 to 6 and from 9 to 16)
1- Put Rom in your device
2- Enable Developers options in your phone
Go to Settings / About Device / Software Info and tap on Build Number 10 times to enable Developers Options.
Then Go to Settings / Developers Options and Make enable "USB Debugging" and "OEM Unlock".
3- Make a backup of you internal SDcard and your data.
4- Power off your device
5- Reboot into Download Mode
(Press and Hold Volume Down + Home + Power button)
6- Open Odin 3.10.7
7- Put BOOTLOADER for G928F in BL
8- Put MODEM for G928F in CP
(For other G928 variant please search, download and flash your Marshmallow Firmware with Odin in AP)
9- Put TWRP RECOVERY in AP
10- Connect device to PC and it added in Odin
11- Go in options tab and uncheck autoreboot (check only F. Reset Time).
12- Click on Start to Flash the files
13- Once it's completed and you see "PASS" in a green box, disconnect device and long press Volume Down + Power
14- Once screen turns off, immediately press Volume Up + Power + Home to reboot to recovery manually.
15- Once in Recovery, install Audax Rom and in Aroma installer select WIPE DATA.
16- When device reboot seems like a Bootloop but is normal. Than start Samsung bootanimation. Complete reboot ends after 7/8 minutes.