restore database using impdp full back
Data Pump uses directory objects. Read this:

Default Locations for Dump, Log, and SQL Files

First create the directory object as:

create directory dump_dir as '/home/oracle/rmanscripts/dumbbackup';


Then you can use that in your impdp command:

impdp full=y direcotry=dump_dir dumpfile=sysfull.dmp logfile=full_db.log


Also:


  while database is not mounted


By this I hope you mean it is open. Data Pump needs a working database, even if it is empty.