I am signed in on my tv to appltv and i get series shows but i cannot buy any movies.ies

An Apple TV+ subscription gives you access to Apple TV+ content (Apple Originals). Other services in the Apple TV app are not part of that subscription, but can be available through the matching Apple ID account.

Unfortunately, currently the Apple TV app on Fire TV devices does not support in-app purchases. You will have to make the financial transaction on a different supported device.

On Amazon Fire TV, Android TV, and Sony TV devices, you can't purchase content from the Apple TV app. You can buy, rent, or subscribe on another supported device and then watch in the Apple TV app on your Amazon Fire TV, Android TV, or Sony TV device. [1]

Movie purchases can be made on an supported Apple device, or in the iTunes application on Windows, or in the Apple TV app on other supported third party devices (e.g. Roku, LG, Samsung, Vizio, PlayStation, Xbox).

The Apple TV+ subscription covers all shows and movies under the Apple TV+ banner, you can't and don't need to buy the Apple TV+ movies separately.

To buy movies from other studios or production companies that would not fall under the Apple TV+ subscription, you can select the price on the movie and follow the onscreen prompts to complete the purchase.

Ahh, totally missed the FireStick tag line. 🤦🏻‍♂️