My dad 53 yrs old is now arguing for everything, acting like a kid, crying, who was the most respected person in our family. How to cure him?

DEPRESSION. Looks like he is having depression. Reassure him that everything will be ok. He is the head of the family and everybody respects him. If the psychotherapy does not work, then he needs anti depressant rx. Good luck!
Needs evaluation. There may be several very different reasons for a person's sudden change in behavior. An evaluation by a doctor is warranted. Behavior change could be due to neurologic disease, psychiatric diseases, or drug addiction.