You cannot "jump" directly from an old version like 5.0 to 6.0.14 without risking a configuration crash. You must follow a specific sequence.
The latest firmware for the Fortigate 200D, version 6.3.4 (or later), brings a host of new features and improvements. Some of the key enhancements include: fortigate 200d latest firmware extra quality
However, "extra quality" firmware cannot create new hardware. If your throughput demands exceed 500 Mbps with all security features enabled, it is time to migrate to a FortiGate 80F or 100F. You cannot "jump" directly from an old version like 5
execute backup config tftp <filename> <tftp_server_ip> version 6.3.4 (or later)
Many users and engineers recommend remaining on 6.0.17 or 6.0.18 for the best balance of late-stage security patches and stability.