Increase in temporary tablespace while import
The size needed in a temporary tablespace depends on the data volume manipulated, but including potentially other actions also requiring temporary space. What you should be doing is this : monitor temporary tablespace usage, (temporarily) expand the temporary tablespace. 

Maybe, you need to recreate your temp tablespace. That is, if there is corruption of some kind. One way - but not the only one - is stopping the database, rename the file(s) of the temporary tablespace, tail the alert.log, and startup the database. Obviously, don't do without backup, and don't test this on production.