how do I calibrate the sensors using the app DJI go 4?  I can't use the assistant 2 firmware because it freeze everytime, so how can I calibrate through the app?

Hi Picanoc Jack, the vision system can be only calibrated via the DJI Assistant 2. Please try to reinstall the DJI Assistant 2 on your computer, download the latest version from https://www.dji.com/mavic/info#downloads, if the application keeps freezing, you may try to calibrate in a different computer.