Is there a way to transfer some photos/videos from Google Drive to Google Photos (same account) without the need to download all the files and then uploading them again?
You can try enabling in Drive settings - "Automatically put you Google Photos into a folder in My Drive". This will show Google Photos folder. Try copying there some photos and check a bit later if they will be shown in Google Photos. Can't promise though :)
its as simple as uploading images from your phone to google photos
- On your computer, go to photos.google.com.
- At the top right, click Upload and then select Google Drive.
- Find and select your photos.
- Click Upload.