so im having trouble with the fab key for some reason its not unlocking the car so i pulled off the key and opened the door manually for some reason the car wont start and everytime i press lock it makes a beeping noise and the start light starts flashing can anyone enlighten me

 

For starters place the fob in the slot just to the left of the steering wheel. This should start the vehicle after you push start. More than likely your fob battery needs to be changed.

 

yup i did that and its still not starting when the door is open the startbutton and the red key indicator in the dashborard flickers and when i close the door i can hear like a rapid tapping noise so im not sure whats wrong and the headlights doesnt turn on and the lights inside the car is very dim

 

How old is your car battery? Can you jump start it? My bet is dead battery especially if it's the original.

If you end up replacing it, don't get a new one from a Nissan dealer. You really want to get something with a higher CCA rating, 640-680 would be fine.