Thank but sry in which way you can save backup to txt file and restore it ?
Hispa
this is possible with a personal web server, as described in the documentation
https://ottnav.github.io/faq.html#backup-directly-to-your-server-for-you-andor-your-clients
use BACKUP VIA API in the backup options and enter "http://127.0.0.1:8080/backup.php". that create a backup file with the name "backup.nav". reload the file with restore via API.
the advantage is that you can create as many backup files as you want by renaming "backup.nav"
I am using an old and very light php web server for android. the app is unavilaible on google play strore but already exist in apkpure
https://apkpure.com/server-for-php/com.esminis.server.php