This article provides some tips for planning a Beyond Visual Line of Sight (BVLOS) flight.
For the special case where you have to fly behind a mountain or tall building (i.e., a mountain or building is reaching higher than the flight height), the safe return-to-home logic ensures that WingtraOne will not collide with the obstacle in case RTH is triggered while being behind the obstacle. In case you would like to fly with a direct RTH, make sure the minimum RTH height above home is at least 20m higher than the tallest object between you and any mission point.
Flying BVLOS means that the telemetry link between the drone and the ground station will get lost at some point during the mission. In order to perform the flight and prevent RTH, you likely have to increase the "connection loss timeout" (see: Safety parameters) and will fly blindly. Such a flight is considered highly risky—make sure you know what you are doing.