Flyboy is right, and it'll come over time.
I have noticed it quite often too, with new hydrofoilers, they can ride with the board sticking "up" in a crazy angle.
Especially with low AR wings like the Double Agent.
The reason is,beginners (have to) use maybe 2 or 3 sizes bigger kites than necessary, so they can "hang" under the kite, going really slow, but without stalling the wing totally.
This also answers your other question papasmerf, the turbulence you can feel or hear, is because the wing is semistalled.
Meaning it rides at a higher angle than it should, but the power from the kite can keep you there.
Untill suddenly it drops down again, stalled.
A low AR wing can ride at extreme angles, without stalling, that is the plus side.
But it does not ride correctly, very inefficient and needs lots of power, and it has huge drag in this state.
Nothing wrong with your mast, a short or long will all work.
What you experience is pretty normal when learning.
Just keep going, learn to ride with smaller kites gradually, as then you can ride the wing and board at the "correct" more flat angle now, without going too fast and getting out of control.
You could also add some line extensions, as this will give you the ability to get power to start, and then easy to ride level because of a smaller kite.
Short version is, you are too powered, and you push the board too much up, to be able to ride without going too fast either.
As Flyboy wrote, very subtle adjustments on your weighting is needed and difficult, will take a long time, but suddenly it works