As a requirement, I need the respondents to be able to submit a csv/xls. Is it possible to achieve with ODK?
Welcome to the ODK forum, @eka We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a real picture as your avatar because it helps build community!
I encourage you to check the documentation as you can find most of the things there.
ODK support file upload from the device. Check this link.