I'm confused as to why this question was closed. The reason behind the question was programming related and is clearly regarding software commonly used by programmers. Any tips how I could improve it.
It seems pretty clear to me that that's not a programming "problem". That your app is creating a CSV file and you're opening it in Excel and the results aren't what you're expecting has nothing to do with your programming nor will it (probably) have a programming solution.
This problem would certainly be faced by anyone who has a CSV file with large amounts of data in the fields, not just programmers.
It would be very much on-topic at Super User.