what does this mean?Thx,
+ Use staircase intonation.
Let those sound groups floating on the wavy river in the figure flow downhill and you'll get the
staircase. Staircase intonation not only gives you that American sound, it also makes you sound
much more confident.
so what does" in the figure flow downhill "mean?and is"flow"a noun or an adj here?Thx,

Question

what does this mean?Thx,
+ Use staircase intonation.
Let those sound groups floating on the wavy river in the figure flow downhill and you'll get the
staircase. Staircase intonation not only gives you that American sound, it also makes you sound
much more confident. 
so what does" in the figure flow downhill "mean?and is"flow"a noun or an adj here?Thx,

Answer

"in the figure" is a prepositional phrase telling you where the sound groups are.
 "flow" is a verb. ("to move in a stream")
"downhill" is describing where they're flowing.

Hope this helps!