If you choose High Quality, then it will upload unlimited photos with free storage. If you choose to upload at full size, then it will take your Google Drive storage space. The application will prompt you with folders to backup and the resolution in which you want to upload the photos. You just need to download the desktop application from Google Photos website and sign in to your account. So, you can avoid waiting for a longer time by using 'Google Photos Back' i.e. If you have a hundreds of photos to upload in your hard disk, then it will take time to upload them one by one.
The first issue is related to uploading speed. Here are the Six Issues With Google Photos And How To Fix Them: Unfortunately, there are some issues that don't work as expected. It has a useful smart search that allows you to find any photo in your library without any major problem. Google Photos is an awesome photo backup application provided by Google Inc.