@LaiSums: For peace of mind, I recommend covering your bases, and backing up to your Samsung account, Google account, and to Smart Switch on your home computer. To being with, please head to Settings > Accounts and Backup > Samsung Cloud > Back up Data, followed by Google Drive > Back up Data. Once you're happy that the back ups have completed successfully, please follow the link, click on 'How Do I Get Smart Switch On My PC or Mac' and download the relevant version.
Once installed, open Smart Switch, connect your device using a USB cable, click on the Backup tab, and follow the on screen prompts. With these steps completed, you can look at removing some personal media from your phone to free up some storage space. If you'd like to double check that your photos and videos have backed up successfully, swipe up from your Home Screen, tap on the Google folder and select 'Photos'. I hope this helps.