Hello kartik37,
From what you've shared it sounds like you're experiencing performance issues with your iPhone, and we'd like to get you pointed in the right direction for a resolution. Get started with the guidance listed here: About iOS performance on your iPhone, iPad, or iPod touch
These steps will help you ensure that your iPhone is performing as expected. If the issue persists, and you believe recent changes in behavior are related to your repair, we recommend contacting your service location directly for additional information.
Take care.