How do i get my monitor to gp back to vertical position?

You can use the screen rotation or tilt control to align it perfectly. Do the adjusting slowly. You may well find that the left illuminated screen area reaches the left edge of the physical screen before the right edges correspond. In that case, you need to go back and tweak the horizontal location control. The same applies to vertical adjustment. Start with one dimension, horizontal or vertical. Expand the illuminated screen image until one edge just meets the corresponding physical screen edge, then go back and tweak the location until the illuminated image is again centred then expand the image a little more. The idea is to end up with both edges of the illuminated screen image each just meeting the corresponding edges of the physical screen simultaneously as you adjust the size.