What should I do if the camera image quality is not good?

Action camera means point-and-shoot, not digital cameras or mobile phones. They're small, light, and easy to swing around. The quality of the footage is not its major advantage.
If the quality of the video is unacceptable, please reset the camera turn off the image stabilization function, and try to record videos in an environment with sufficient light in 4K resolution. 
When you preview the footage on your phone through the app, you are only previewing a very low-resolution version of your actual footage. You could try to preview them on PC.  If you're still unsatisfied with the video quality, please send us some pictures or short videos to the email box（ cs@akasotech.com ）for our reference.