Depends on the purpose and make of the helicopter.
A fast aeroplane will be faster than any helicopter, but a fast helicopter can be faster than a slow aeroplane.
The fastest are attack helicopters like Apache, they mostly fly about 230 -250 mph.
249 mph
A typical medivac helicopter flies about 160 knots.
It can fly at 224 kmh - approximately 130 mph.
The Chinook can fly at about 195 mph.
For a fairly new helicopter, around 120 knots. Around 150 mph, except for fast military helicopters.
quite fast, there is more drag from the fuselage going side ways and it would be less stable
the original AH-1 Cobra flew at 170 mph
There are many different helicopters. Most small civilian helicopters may fly for about an hour, but large passenger or military helicopters can fly for 6 hours or more.
Sadly Not, it's physically impossible.
Much more complicated than a fixed wing aircraft. -Military helicopter pilots in most services MUST qualify as fixed wing pilots before graduating to helicopters.