can we recover before overwritten file.
Before for sure, after might be more difficult.
If you mean, can you recover deleted files which have not yet been overwritten, then yes. If you're using Windows, you could try something like this.
i replace my file with same name another file now i want to recover my file which was overwritten.
Of course, you can recover lost data. And i want to say overwritten is a very dangerous thing for which might cause permanent data loss.
Once you find your data is gone, take quick actions to get them back or you might lose them forever.
Here is a detailed information for lost data recovery:http://www.easeus.com/mac/mac-data-recovery-resource/free-mac-os-recovery-software.htm