How to get and update value on a specific cell?

I want to get Value of a specific cell (like A4) and Update the value of a cell in a particular row and column on spreadsheet. How can I do this? Please someone help me.

create as variable and when it update call the value, or you can specific with row number.

If you want the spreadsheet to be external to the app, you can use Google Sheets or Airtable (see this: