Cant download apps

That means there some type of issue with your payment method, and it cannot be verified.

Either there's a pending charge, the payment method was unable to be charged for the current purchase, or there's some data missing from it and it is not verifiable without it.

You must ensure the payment method information is correct, and that the payment method can be charged. iTunes will place a $.99 hold on it, which is reversed once it is successfully applied.

See here for more details: If your payment method is declined in the App Store or iTunes Store - Apple Support

Free apps are free... so you don't have to pay for them, but you need a payment method to downolad those apps. See the following support guide:

Payment methods that you can use with your Apple ID - Apple Support

Regards

Giulio