Hi roy39!
Sorry for the unexpected message but have you tried uninstalling apps?
No worries, if you have lots of photos I would recommend to delete some, you can delete any number in your choice.
Mind telling me what your one ui is?
No worries, might be a app that takes lots of storage,
Or this could just be a error, for more info go to samsung website. Thanks!
(I'm sorry I clearly didn't find anymore ways, but have fun!)