How can I automate this process?

How can i make this widget 100% automatically?

I have intergrated my form with google spreadsheet. But i cannot use that google spreadsheet in my google drive account to lookup data. So I need to download it and save it in .xlsx.

Is there is any solution for that?

From how I understood it, you wanted to automate the process below:

JotForm > Google Spreadsheet > save as Excel > import to Spreadsheet to Form Widget

Sadly, this can't be done technically speaking. The process needs to be user-initiated. The Spreadsheet to Form Widget can only be setup in a way that the form owner will upload an Excel File to the widget wizard. Only then will the widget have a way to query/lookup data from a sheet.

Related guide: How-to-Use-the-Spreadsheet-to-Form-Widget 

In case we misunderstood your question, just get back to us with a bit more info and a clearer description of what you're trying to do so we can better assist you.

The part "save as excell"... can the data be update automatically?
...

Let me give you an example.
My customer fill in the rental form. So i want to create lookup function by
their id number..
So i already have existing customer data in google spreadsheet. But this
google spreadsheet cannot be upload in jotform..
It need to be download as excell first.. then upload in jotform.
So how can i make data in excell update automatically everytime new
customer enter the data?
...

That is not possible, we do not have an automatic feature that will pull data from a database. What you can do is to hire a developer that can create you the proper script solution to pull data from your own database, and also forward any new entry to it. 

I assume that your developer will need to download your form's full source code: https://www.jotform.com/help/104-How-to-get-the-Full-Source-Code-of-your-Form 

Here is an example on how to forward data to your own database using MySQL and PHP: https://www.jotform.com/help/126-How-to-send-Submissions-to-Your-MySQL-Database-Using-PHP