I am very week physically and mentally .how can i make my self better?
Hard to tell
Weakness may reflect a lack of exercise or symptom of underlying medical condition: diabetes, thyroid disease, occult infections, anemias, post viral syndromes, muscle or joint disorders, vitamin deficiencies, malignancies, nerve disorders, heart, lung or kidney disease, or depression.
The list of possibilities is exhaustive. A good history and exam by doctor may direct you to better health.