I had infection in intestine. doctor cut that part out and steatched intestine. i want to know how long it take to heal and what are precautions?

Variable: Without a full history and physical exam and access to prior medical records this is impossible to predict. The best person to assess this and respond intelligently to your question would be the surgeon who performed the procedure. Go back and ask them.

Healing time: Healing time for any operation is 6 weeks. 6 weeks is when any area in your body has 80% of it's maximum strength. You most likely have an abdominal incision which is prone to developing a hernia. Precautions include no heavy lifting greater than 10 lbs. And no abdominal or core exercises.