Database files never reduce in size automatically.

Don't run that backup with truncate only. That's just a log backup which doesn't write the backup file, no special magic in it. However it breaks your log chain and reduces your ability to recover

Don't shrink logs to 1. Hell, make that don't shrink logs without a good reason. If your log file needs to be a particular size for regular operation, leave it that size. Shrink/grow/shrink/grow just wastes time.