WILDFIRE72,
Run dxdiag.exe save the report and upload it. Also start the arma launcher and options then export launcher logs to desktop and also upload it. last run the arma3 troubleshooting report and also upload it. I need to see what you have and what is loading.having seemn this before it could be several things, so I don't want to guess.

ok the files are uploaded...

WILDFIRE72,
First NOTE ! New drivers as of yesterday for you.
http://www.geforce.com/drivers/results/96877
Looked over everything for what is causing the problem. I noticed you are not playing a single player or multiplayer, but something in the editor that you made, correct? Just a question. Are you running in SLI mode, as Arma3 doesn't support it. I also just thought of this after writing everything else, so going to put it here first.
NOTE ! : Try this first.

1. right click on desktop and open Nvidia Control Panel
2. 3D setting- Adjust 3D settings
3. Click on program settings tab
4. Select a program to customize
5. Pick Arma3 from list
6. go to CUDA -GPUs
7. from the option on right pick the GTX 980 ti
8. go to Multi display/ Mixed GPU acceleration
9. Pick single display performance mode
10. Click apply and close control panel.

Ok start Arma3 with no mods, no command line options ("E:\Steam\steamapps\common\Arma 3\arma3launcher.exe" -no Benchmark -noLogs -noPause -enableHT -malloc=tbbmalloc), no checked boxes in the launcher-advance.
Yes do it please this way first. The reason is you have way to many things going on at the same time. To check Arma3 for issues it is better to disconnect from your pc everything, but a keyboard, mouse (one only) and are using one videocard (not overclocked) cpu ( not over clocked ) all windows updates done.
Yes I know it's work, and you may have try this or not. The reason I'm bringing this up is, you have several usb devices, two video cards, two monitors, internal sound, and nvidia hdmi sound, multiple hard drives.
You see the problem with trying to figure out what is causing the problem with Arma3. I'm not saying you cant run your system like that, it just makes it harder to figure out the solution.
From what you said "strange graphic artefakts very pixeled,after 10-20 minutes freez...back to 3d editor same framerate of 1-2". Yes?
This is why I'm having you change the setting in the Nvidia Control Panel and loading the game vanilla version only. Also set the videocard to the factiry clock speed.

I'm going to look at the videocard first. Here is what the card should be clocked at per Nvidias website.

GTX 980 TI Engine Specs:
2816 CUDA Cores
1000 Base Clock (MHz)
1075 Boost Clock (MHz)

GTX 770 GPU Engine Specs:
1536 CUDA Cores
1046 Base Clock (MHz)
1085 Boost Clock (MHz)
What manufacturers do is increase the clock speeds of their cards for customers. Yet for some reason some games look for the clock speed based on the drivers from Nvidia. So running your videocards at a higher clock speed could be the cause of the lower fps after a few minutes.

If you videocard came with software to change the clock speed open it and change it to the default for the card too. If not use OC II software for setting the clock and voltage of videocards.

the Problem was solved with one of the former updates (which one exactly I can`t tell, cause I had no time)...sry..... but!!

... with the DEV update yesterday 12.01.2016 I get the same issue... as mentioned before... appr. 13min. and then drop of framerate to 1-3

maybe there is a connection to the report of DnA:

ENGINE
Added: Aligned allocators are back on Dev Branch. Please report any significant new slowdowns / performance issues