Hi @jagajith23, welcome to the forum 
Apologies for the delay on responding to this - I’m travelling at the moment along with several other members of the team, which has made fast turnaround on responses quite difficult.
That issue sounds potentially the same as this one, so I’d recommend reading through that and trying some of the suggestions there.
Precise positioning requires some form of positioning system, or at least a velocity sensor) for somewhat accurate movement estimation. It’s possible to use the flight controller’s internal accelerometer for very rough movement estimates, but positioning error grows quickly with double-integrated quantities that have no source of feedback.
I’m not certain what you’re referring to here. Are you saying if you don’t add a delay to your code it doesn’t work, or that your commands stop working after some amount of time (that you’re referring to as a delay)? If it’s the latter, you’re most likely running into a failsafe that you’re not handling correctly.