Dumb trainers with Garmin Vector 3

Just started to use Zwift , I am setup in a dumb trainer , connected with Garmin Vector 3 and Wahoo heartrate strap.
I seem to work well going up % grade but on the down hill I have to work harder any idea’s ? Am I doing something wrong?

Unlike a smart trainer, a dumb trainer won’t know you’re going down hill, so I’m guessing that’s why.

You’re changing gears to mimic resistant on your trainer and seeing your power on the screen through the Vector 3?

Strange because yesterday at the end of a ride I tried to stop at the top of a hill to join my 2 friends on smart trainers and I over lapped the top… the following was to laugh at. I stopped pedaling got off my bike snd the avitar flew down the the hill at 50kph…for 6km. Found it to be a bit of a joke… knowing that next time I will stop pedaling and rest when I am in a group ride.