If the missing sections are always in the same part of the screen it may be that the appropriate connections to the display panel are faulty, the connections within the display panel itself are faulty or perhaps there is a problem with the motherboard.
How old is the phone?
There is a 1 year limited manufacturer’s warranty on the phone. If the phone is still within the warranty period, consult the warranty as to what to do to make a claim for a manufacturer’s warranty repair or replacement.
If it is no longer covered by the warranty, you could try opening the phone to inspect the connections between the display panel and the motherboard. If they appear to be OK then the problem may be in the display or perhaps in the motherboard. Either way without a schematic diagram it will be hard to find out where and if the problem is in the display panel it will have to be replaced as they cannot be repaired and finding the correct panel may be a problem in itself."