So everything worked for me on my last flight. The plane, while AP was engaged, recognized I was descending and once I past DECL way point I noticed it was slowing its self down and automatically, changed its speed to about 200kts from 290. Once I was approaching the runway I turned AP off and the plane still slowed its self down and changed its speed to 132kts for landing.
The only thing I did this time was I made sure to click the “engage manage speed” knob. Not sure if that is the fix but that is worked for me. Even though it already reads that it is engaged with the three dash lines I still clicked it.
Thanks for the advice!