Learn a bit more about the file manager.
Why can't I merge my files?
Ensure that the files you are trying to merge use the file extensions .csv or .xlsx, and that they contain no more than 1 worksheet. If a file contains more than 1 sheet, you can split the relevant sheets out from the original file, then merge those single sheet documents together into one cohesive file.
Why can't I split sheets out from my file?
Ensure the file you are trying to split uses the file extension .csv or .xlsx, and that it contains more than 1 worksheet.
Anything else on your mind?