I lost my iPhone my phone is in offline so my friend search in find my iPhone but when he alert it in lost mode it never became online what can I do?
You can check your service provider to see the last location it detected your phone in, and you can search that area. Unfortunately, if your iPhone is offline there is nothing you can do to find its currently location.
Read the procedure listed here: https://support.apple.com/en-us/HT201472 for information on how to report your iPhone as lost and what to do (change passwords, etc.).