Fixing a garage door that has come off its tracks can be very dangerous and is not recommended as a DIY project due to the risk of injury or further damage. However, to give you an idea of the process, here's what a professional would typically do:
Inspection: The first step is a thorough inspection to determine the cause of the problem and assess the damage. This could include examining the rollers, tracks, cables, and springs for signs of wear or damage.
Door Securing: If the door is stuck open and off its tracks, the technician would secure it in place to prevent it from falling while work is being done.
Track Realignment: The tracks would be checked for alignment and straightened if necessary. If the tracks are bent or severely damaged, they may need to be replaced.
Roller Replacement: Any rollers that have come off the tracks would be reset into the tracks. If the rollers are damaged, they would be replaced.
Spring and Cable Check: The springs and cables would be checked for proper tension and operation. If a spring has broken or a cable has snapped, it will require replacement with the door in the closed position.
Testing: After repairs, the door would be manually tested to ensure smooth operation. Adjustments would be made as needed.
Opener Test: Finally, the automatic opener would be tested to ensure it is synchronized with the door's new position and operates correctly.
Please note: The tension in the springs and cables of a garage door can be extremely dangerous. If they are not handled correctly, they can cause serious injury or even death.
Given the risks, and because your photo indicates a severe issue, I strongly recommend that you contact a professional garage door repair service. If you are in San Diego, you can reach out directly to your own service at 619-715-0159 for assistance.