Hi i_maq,
When you make a change to the camera's position in the 3D Preview, be sure to click on the "Copy this view to the current render camera" button at the bottom right of the 3D Preview pane. This updates the camera's Position and Rotation values under the camera's settings.
If you plan to have an animated camera with several keyframed positions, you'll also need to click on the buttons immediately to the right of the Position and Rotation labels and choose one of the options from the context menu to Set Animation Key > Key All (or Key X, etc.). Same thing applies to the Rotation channels. Also, be sure you're on the correct frame when you do that, because you're setting the keyframe value for that frame.
Kevin
