1. Try to login to database with SYS AS SYSDBA user. If the instance is idle, run the startup command.
2. If ORA-03113 occured, check the latest error in log file, C:\Oracle\diag\rdbms\SERVICE_NAME\SERVICE_NAME\alert\log.txt
3. Error description:
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim X bytes disk space from X bytes limit
4. Login to database with SYS AS SYSDBA user and run startup mount command.
5. Check the current recovery file size limit with query: select space_limit/1024/1024 as limit, space_used /1024/1024 as used from v$recovery_file_dest; 
6. Change the limit with command alter system set db_recovery_file_dest_size = 30G scope=both; run COMMIT; 
7. Run shutdown and startup commnds.
