Brake trouble on my 97 GMC Jimmy 4X4 NEED HELP ASAP!!!!!

I have a 1997 GMC Jimmy 4X4, my brakes are very hard to push and also makes a hissing noise, even then it doesn’t stop the car, also when you press the brakes all the gauges in the dash move, it also acts like its going to stall? what could be causing this and what can I do to fix it? Or what could be causing this?