Hello,
Configuration was be optimized as follows :-
1. review config for unsed services, address objects, certificates, policies, VPN and any other settings and delete them if they are not needed.
2. Summarize static routes if any in the config.
3. combine polices on the firewall to reduce the number of polices and related objects on the firewall.
Regarding config backup, are you able to download / run the command " get tech". if yes, then that usually has a complete config file as well.
Regards
Vatsa