If you are interested in learning more about DIY garage door repair, it might be a good idea for you to watch this video. In the video, they are dealing with a situation where a bottom board has rotted out on a garage door, and it is attached to the bottom rollers. The one side has come off, and the other side is actually still intact.
Basically, the wheel is being flexed, and the door is not able to come down like it is supposed to do. What they are trying to do is replace the bottom board and have everything put back together in a way so that the garage door can function again. They then detail the process.
In some cases, you will be able to do a garage door repair project on your own, depending on what is actually wrong with it. In others, it might be a good idea to contact the professionals to take care of the repair for you. It really depends on the situation, but you do want to make sure that you do not cause any unnecessary damage to your garage while you are trying to fix it.