Its called Keystone and there is an adjustment in the projector to eliminate it but its not recommended to use it as it degrades the picture because you no longer have 1 to 1 pixel mapping. One option is to tilt the top of the screen out to match the upward tilt of the projector keeping it perpendicular to the screen. I take it that your room or wall is not wide enough to set the speakers to the side of the screen. Optimal height of the screen is your eyes should be about level with 1/3 of the way up the screen, it looks like yours will be mounted too high.
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