If I understand your situation correctly, you want to create 3 new packages to better organize your functions, but in copying the functions over to the new packages, this is introducing name-conflict errors.
As per the [rules for developing custom functions](https://community.denodo.com/docs/html/browse/8.0/en/vdp/developer/developing_extensions/developing_custom_functions/developing_custom_functions), functions with the same names are not allowed. So across all of your packages, there must be unique names for all functions and no duplicate implementations. With this in mind, one possible solution I can think of in your situation would be to create those 3 new packages with their respective functions, but then delete the implementation of any “Date”, “String”, and “Internal Processing” functions from the original package, so they are not defined more than once. That however would involve altering/deleting the original package, which as you said, is out of the question.
So I believe the only solutions would be to either alter/delete the old package, or change the function names in the new packages so that there is no conflict.
Hope this helps!