After Unpacking the zip Files of my Google Photos Takeout, I found the Metadata in json files and Photos without the Original Modification Date.

Using exiftool on mac I managed to Re-Import the EXIF Data and Adjust the Date to the Date of the Photo taken

1. Install exiftool command
https://sourceforge.net/projects/exiftool

2. adjust the folder path in the dir variable containing your unpacked Google Photos export data

3. Run This One Line Command in Terminal and it will and apply the json File Info to the related photo:

dir="/Users/islam/Downloads/my_google_photos"; exiftool -m -r -d %s -tagsfromfile "%d/%F.json" "-GPSAltitude<GeoDataAltitude" "-GPSLatitude<GeoDataLatitude" "-GPSLatitudeRef<GeoDataLatitude" "-GPSLongitude<GeoDataLongitude" "-GPSLongitudeRef<GeoDataLongitude" "-Keywords<Tags" "-Subject<Tags" "-Caption-Abstract<Description" "-ImageDescription<Description" "-DateTimeOriginal<PhotoTakenTimeTimestamp" -ext "*" -overwrite_original -progress "-filemodifydate<PhotoTakenTimeTimestamp" "-filecreatedate<PhotoTakenTimeTimestamp" --ext json "${dir}"

Finally, you can delete json Files

dir="/Users/islam/Downloads/my_google_photos"; find  "${dir}" -name "*.json" -type f -delete

I have similar working solution for Flickr Export too.

Google Takeout Link: https://takeout.google.com/