Hi zeljko.bobictuw366, welcome to Thunkable! 
Be sure to check out How to ask Great Questions v2.0, the Community Guidelines, and our Getting Started Guide to make the best of your Thunkable Community experience!
While we don’t have a good way of importing CSVs right now, what I would recommend would be to import and export CSV through Google Drive. That way you can connect your Thunkable project to that Google Sheet afterwards.