im not able to download anything , even the free apps.

A valid and verified payment method is required to access the iTunes and App store services including downloading free apps. Specially if this is a brand new Apple ID that was just created, or there was an issue with a previous purchase that could not get correctly charged.

You will have to add a payment method to the account to verify it. It will not charge you, though may place an authorization hold on the payment method for verification purposes. This hold should be reversed shortly.

Once the payment method is correctly verified, it can be removed and will not ask for it again unless there is a problem again when trying to purchase an app.

See here: Change, add, or remove Apple ID payment methods - Apple Support

and here: About payment card authorization holds from the App Store or iTunes Store - Apple Support

You need to verify your payment method of choice, even for free apps. This is a one-time process and it will never pop up again after you are done.