With the pictures I've looked at of the Ryze Tello, it seems that the camera is fixed and cannot look straight down, such as with the DJI Mavic Air 2. Does the camera have variable angles, or is it fixed-angle?
The Ryze Tello has a fixed-angle camera and is not adjustable (without modification). There are, however, a few ways to get pictures at different angles. The first way is to accelerate to get a downward camera angle or to go backwards to get an upward angle with the camera. This method is great if you don't want to modify anything. If you want a permanent adjustment to the camera angle and you don't mind modifying the Tello, you can follow the instructions here to modify the camera position.