Sandeep,
You mean 011 49….? Or also +49 should work, not just 49.
If your friend’s number is a mobile phone then 711 won’t work because, as mentioned on our page on how to call Germany, geographical area codes are used with fixed numbers only. I don’t know why your friend would give you an incomplete cell number, because these numbers can have different prefixes across Germany (15, 16 or 17), and there is no way for you to guess which one to use. Again, if this is a mobile phone.
I would contact this person in some other way and clarify this.