You can’t fully see it in the video, but the downhill incline here was quite steep. After handling a few like this, you start to get used to it: you tilt the wheelchair as far backward as possible, shift your body weight back, and move slowly.
If you have someone behind you holding the wheelchair by the handles, it is/feels much safer.
If you’re traveling in Morocco and facing a downhill like this, take it slow and steady. And don’t hesitate to ask someone nearby for help – often, you won’t even need to ask. People will notice and quickly offer to assist. I’m not exaggerating – kindness here is abundant.