If the door is still on its tracks and just binding, you can sometimes free it by hand with the opener disconnected - pull the release cord, work the door gently, see if it seats back in. If it's fully off the track, stop. A door hanging on one cable with the other roller loose is under spring tension that can let go without warning, and torsion springs on a standard double door hold enough force to break a bone.
We'll say it plainly: this is not a YouTube repair once the panel is actually derailed. The honest DIY move is limited to the opener disconnect and a visual check - track gap, bent rail, a roller that's clearly cracked. Past that point you're guessing at spring load with no way to measure it safely.