i forgot my backup password

These are the only steps you can perform (section "If you can’t remember the password for your encrypted backup"):--> About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support

Regards

Giulio

Note that resetting the backup encryption password does not change the password of your existing backup(s). So if you are trying to restore from a backup and needing that password, you'll have to figure out the password in order to use it.

If you are simply trying to make a new backup. Then follow the instructions in the link/section provided by ProustGiulio, but for #2 the support article is currently wrong. You need to tap Reset ALL Settings

(Resetting Network Settings does not reset the backup encrypted password)

Thanks for your clarification, Chris0107 :)

Giulio