Can you help me how to trace my iPhone even if its offline?

See this link --> iCloud - Find My - Apple

This presumes you enabled Find My on your phone. If you didn't, you can't track it.

See this link for what to do if your iPhone is lost or stolen --> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

apart from what you can do in find my iphone in www.icloud.com

you can report the IMEI to the carrier and have them block it

in some countries reporting the IMEI to the police will have them block it from all carriers