Hi asti56,
I have just built a small hump yard to test this and it works.
Place a trackmark about 25 metres down from the top of the hump and give it a radius of 1 metre. Place one more trackmark where you want the shunter to start from. The commands you require are UnCouplez From 66277:80000 and UnCouplez 66277:80005 by smileyman and Stop Train 131986:150150 by atilabarut. Then the order of commands from start position. Drive to trackmark Hump, UnCouplez From xx, stop train, drive to Trackmark Start, Stop train, Drive to Trackmark Hump, UnCouple From xx, Stop Train, Drive to Trackmark Start. And repeat this as often as required. Note If you are using a deisel shunter or a steam tank the car next to the loco is number zero, if you are using a steam tender loco the car next to the tender is number one. Also make sure you give the UnCouple command before the Stop Train command at the top of the hump. Hope it's not too cold in Germany these days.
Hope this helps.
Bill69