I notice some of mine appear to be duplicated; think this is caused by being asked on my mobile to add photos, and the photos that Google select have already been added (which of course I can’t remember).
It may happen that Google Maps (through Google Photo) ask you to upload a photo that have been already uploaded directly when taking the photo, but this is usually happening only once. I see that you have some photo that has been uploaded four times, like this one.
Please try to check if it happen again, to help Google Maps Team to better understand what is not working properly, and post a screenshot here.
If an opportunity arises, do feel free indeed to check the steps provided by @ErmesT .
For the moment, if the duplicates happen to be found, you may go ahead and have them deleted.
If it would happen more constantly, do feel free to let us know in the current post (currently it would also be relabeled to How-tos, since it would be more relevant to the main subject).
You may also use the tagging system, with the “@” so that the name of a person you are forwarding the message will appear, as it also allows you to receive notification to follow up posts easily.