how to recover deleted photos from SD card on Samsung S7?

The more you use the phone, the more you reduce the chances of recovering the photos.

The internal storage partition (/sdcard/) is used by apps, as well as for storing downloads, music, photos and videos.

The photos can be recovered as long as they space they currently occupy has not been overwritten by new files, you can check the guide how to recover deleted photos from SD card on Samsung Galaxy to find the answer.