How to free internal memory if no application is downloaded?

I have an Android traveler, RCT6773W22B. This is version 5.0. When I first received it and years later, I could download at least 5 downloaded applications at once and have a large amount of photos in my gallery. I would still have room after that. In time, I would delete applications that I no longer use. If I wanted to download something else and that there was not enough free space, I would delete apps and / or images that I do not need . Now I can not download anything because of the internal memory. I do not have applications, 5 photos (not taken with the camera), and I've cleared the cache on everything except on Chrome. This tells me that my internal memory is completely full and that I can not transfer anything to an SD card. What do I do?