Higher True Air Speed (TAS) at altitude and a strong tailwind is the answer to your first question. Re the descent, the Ground Speed (GS) could increase or decrease depending on the wind direction and strength as you descend through the levels. TAS will decrease on the way down unless you power up going down that’s normally unlikely in most aeroplanes.
I currently fly old 100 series Dash 8s and they are lucky to indicate anything over 160 kts in the cruise, however the TAS at altitude is normally about 240 kts, then throw in the wind effect and the GS could be anything more or less.
Good questions Clint and I hope your doing well these days.