Here are both manuals that are available for the Mantis Q. If you need them in a language other than English try Yuneec.com and select your country at the bottom, they may have the download in your native language.
I got the return thing figured out but something happened today. The drone was not too far away from me and I pressed the return button but it started going away from where it started. What could have caused this? Do I have to do anything to calibrate it?
And when it is returning, how does it know not to run into stuff? Does it take the exact same route it to when going out?
You need to set the RTH height to a value appropriate for the area you are flying in. It needs to be set 10 to 20 feet higher than the tallest obstacle in your flight area. When you activate RTH and your altitude is lower than the set value it will stop its motion and ascend to the RTH altitude you set, then fly a straight path to the takeoff position and land. If it is at or above the RTH altitude setting, it will just fly straight to the takeoff position and land.
If you take off from under overhanging object like a tree, covered patio, or such DO NOT use RTH to land the Mantis Q. Be sure to read the RTH section of the User Manual, not just the Quick Start Guide. It should actually be labeled the Quick Crash Guide because it doesn't give you enough information to safely fly the aircraft.
If you press the RTH a second time it will halt and hover and you can then resume piloting. You get the same result if you use the Land button which lands the Mantis Q at its present position, the second press of that button halts the landing and you resume piloting.