Moto G Power has 64 GB of space. That is a lot of space you are using. How many apps do you have running? Have you tried going through your apps, disabling those you don’t use or need, clearing cache and storage where you can? Have you done all of the updates to your phone? I find that if we don’t do updates storage is used up but once updates are completed, storage is down as well. Have you been storing a lot of photos and/or videos on your phone? Those take up a LOT of storage space. If you do need more storage, an SD Card can be made internal easy enough. There are posts on how to do this. I recently did it with our old Moto E phones before we bought new Moto G Fast phones.
But with 64 GB of storage you are either using an awful lot of apps, saving an awful lot of pictures, videos, or something or haven’t completed all the updates.
You could also try an app like Ccleaner. We have had success with it in our phones many times and we also have used it on our tablets and computers as well. it is safe to use and you can decide what types of files you want it to clean and/or delete.