How to use backup .gz file

/home/chaitunas/immich/backups/immich-db-backup-20250828T020000-v1.139.4-pg14.17.sql.gz

how to use this file and restore it.

Hi.

gz file is compressed archive. sql file is plain text file- dump of Your database. You can restore Your database using sql file simply.

See documentation of Immich:

And take time to explore pg_restore command, or using Adminer (available from AppStore) for access Your database.