Well It's not dangerous, but usually I like to see temps around the low 70's. It shouldn't malfunction at those temps, but try and get them lower as soon as you can. In the meantime, you can try and mount another fan inside the case or turn down your heat.
80C is not dangerous to the card, but i would put it as it would cut down the lifespan of the card (nothing serious, it would die sooner than it would over the years if kept like that, you should have nothing serious to worry about though). You could try turning up your case fans, and turning up the fan on the GPU itself. Hope this helped you out