Spreadsheet processor

I would like to make a web app out of a Google apps script. Here's what it should prompt for the user to upload a Google Sheets file or an Excel file. If the file is in Excel file, it converts temporarily it to a Google Sheets format and The apps script should be executed on that spreadsheet data. The web app then converts The spreadsheet to Excel format and gives to the user. The file name of the completed file should start with "Case Tool" followed by a timestamp in the file name to make it original. The original file should not be changed in any way.I have it practically finished. I just need someone to take my project and help it get past the errors I'm getting.