Is there a certain way to fly a 747 or has anyone had this problem?
You fly it like any other airplane. By pitch and power.
If it's stalling then the pitch is too high and the airspeed bleeds off. Turn the auto-pilot off and fly it.
If you insist on using the auto-pilot before you know how to fly it, then think about why it's stalling. If the auto-pilot is holding the pitch too high, then you need to turn the vertical speed down.
A 747 will hold an incredibly high vertical speed at lower altitudes.. however, as the altitude increases, the air gets thinner and even at full thrust the vertical speed needs to be lowered.
All of this of course depends on the passenger and fuel load.
Fully loaded it should comfortably hold 3000fps well over 10,000msl. Over 20,000msl, you should be climbing at well under 3000fps and as you near 30,000msl, the vertical speed should be near 1000fps or less.
Just keep an eye on the airspeed.. keep it WELL above 200kias by lowering the vertical speed as needed.
It would be whole lot more fun and educational though, if you learned to fly it first, and then use the auto-pilot.
All those hours you spent mastering piloting fundementals in the smaller, slower planes will serve you well ... you'd know what stall speed was, and how not let the plane get that slow