My father is 69 and is diagnosed with mild cerebellum and cerebral atrophy. please suggest the precautions and medications?

Can vary: Causes are several, but if your Dad used alcohol to excess, this could result in a similar atrophic pattern. Generically, might consider a medicine to assist his memory, focus, etc like donepezil, Exelon, (rivastigmine) Namenda, but would also want to supplement B vitamins, especially thiamine. Also, best to discuss further with his doctor.

Fall and balance : Loss of balance and falls are major risk with cerebellum degeneration. Get his gait evaluated by neurologists and physical therapy expert. Get a Walker to prevent falls.