Hiya
I am a noob when it comes to 747's however, i took one from Bangkok to Hong Kong over the weekend. No reason for the location it was just that i wanted to see the difference between the 747 and the 737 i have been playing about with.
I do not know how you fly but as a noob i set up my autopilot while taxiing and kick it it when i gear up.
I tend to just leave speed to 250kt until i reach over 18,000 and then i gradually speed up after turning on the Mach speed. What i mean by gradually is that i just notch up the speed in increments of 5 and just before it matches the setting i continue again. No real reason for this it just gives me something o do while on auto pilot if i am not setting a heading etc

Any way, for my first flight i got her up to FL320 with no issues at all but as i said i do have auto on, my joystick not great for manual.
Now i did save on the start of my decent and i am glad i did because i had the opposite problem to you i got to FL50 and was trying to slow down using the spoilers and nose went up and splash in the sea lol

. I have learnt it may of been a combination of to much spoiler, turning to line up the run way, and flaps. Or trying for 180 is just to slow for a 747, i dunno. But i did have it saved and did it again but a bit more gently on the decent and found the middle of the runway.
I have waffled on a bit, but my advise, albeit probably not worth it, is keep trying but save at say 18,000 so if it does go pear shaped you can load right back in and tweak something different.
I had a similar problem with concorde but i was to keen and just whacked the mach meter up lol.
Enjoy the 747 she is a beauty when u hit the middle of the runway
