You can read about the 7 stages,it's a good guideline.
The arguing and paranoia are the worst part of MIL's dementia. I try not to bring up any of her focus issues (medications or money)
My husband seems to go back and forth between stages on a daily basis. Hard to say what stage he is at. He can be very irritated and in denial and then the next day very quiet and gentle. The irritated days are becoming more frequent and he wants to argue with everything I do or say. I try to keep him busy with simple tasks but when he asks for help I am very short on patience. It just saddens me to see him struggle with some things that used be second nature. I have the feeling I am not good at caregiving as we are just beginning this journey.
You can Google "Teepa Snow's Gems" very interesting description of each stage from a Saphire to a pearl. It is on YouTube. Easy to find. I prefer her gem stages to the regular 7 stages which vary so much it is hard to pinpoint which one your mate is in.