What language should I use for "data processing application"?

In the next few months, I will need to build an app/ daily job that will take data from at least 2 or 3 APIs (potentially growing to 10), clean it and post it into a relational database.

There are no standard rules about how data is coming from the APIs. e.g for a field named socred can be assigned different ranges like 1-10, 10-100, A-Z... etc. The tricky part of this task is to find patterns and categorise this data.

The questions are:

1. Which programming language is the best for solving this problem?
2. Should I just use c# and not thinking about learning a new programming language?

My tech stack: dotnet, javascript, a little bit of python.