Mark the sealing surface of the head with a sharpie then lap the head using lapping compound in a figure 8 pattern... You will see the high spots if it's warped, cylinder sealing surface may need to be done also

Or if your cylinder head stud(s) pulling out? Post a pic of the top of your cylinder

Head gasket need to be installed counter clockwise one stud to get the restricted holes over the exhaust port?