Add New Drywall
Once the frame for the new soffit is up and the electrical boxes for the lights are installed complete with wiring, you need to put up new drywall. Attach the drywall to the new frame with drywall screws.
Note: A new soffit was a better solution instead of trying to patch and repair the ceiling where the wall was removed.
Apply a thick layer of joint compound to the seam, making sure to fill the space between.
Press the drywall tape into the mud, and smooth it out. Go along and fill in each screw head.