Hello Everybody!

My friend have some issues with his 6. He is far away from me, and only can work at nights, so we thanks for any tips.

Problems:
-After a long travel he stopped the car, and some minutes later he can't start the car. Some minutes later the car starts, but the windows and air cond. not worked
-On the way home, the engine weakened, only can go with 90-100 Km/h, then some minutes later stalled. Symptoms the same, plus the radio just light up, but didn't turn on. And if he turn on the hazard light, the radio light flashes like the turn signals, and the same happens with the brake lamps if they activated.

He waited 40 minutes for the towing, during this time he used his hazards. When I arrived the hazards works very faded.
At his home we tried start the car, everything lights up, radio too but didn't turn on, no crank, nothing. After 1 minute, the blue main relay starts clicking, the headlight, taillamp starts flashing in the same speed like the clicks.

We tried:-Cleaned: -battery terminals-Unplugged, replugged main harness in the fuse box-Checked the fuses
-The battery had 11.3V, so tried jumpstart (the battery 2-3 months old)

I run out of ideas, if you have any tips, please help.
Thank you!