There are some parts of your garage door that you can easily fix yourself such as re-programming your opener, re-aligning the safety eye sensors, and tightening hardware to name a few. Other repairs are more complicated and should be done by a professional.
While you can find tutorial on how to fix many parts of your garage door, you need to consider that the equipment is heavy. Also, parts like the springs and cables are under tension. If you break that tension, it can cause damage to your property or harm to you.
You should not attempt to make a complicated repair unless you have experience with garage doors.