So as far as the left and right is concerned, this is due to the attitude that you can also set the game for left-hand traffic, since in most countries there is right-hand traffic.
Going from the right-hand side of the road, you now drag a street in the editor from the left-hand side of the screen to the right-hand side of the screen, then the Untere Straße is the "Forward" and the Obere Straße is the "Backward", i. e. the opposite direction.
Can you show a screenshot of your street so that you can better understand how your street is built?
If you look at the street in the top view, and then drag a street from the bottom edge of the screen to the top edge of the screen, then the "Forward" is the right half of the street and the "Backward" is the left half of the street.
The stop offset must be set in the lane on which the bus normally drives, usually the outermost lane, e. g. the lane on the far right for a multi-lane road.