Hi there @Avastmehearties. You can go under application manager to move as many apps as you can to the SD card and set the downloads to be stored on the SD card per default.
Sorry to hear that. If the phone still gives you an internal storage warning after uninstalling everything with a factory reset (without installing any apps), then the phone may be defective. How long have you had that phone for?
In that case it may still be covered by the warranty. If it has not sustained any physical damage (wet, dropped, broken, etc..), you can contact ZTE at 877-817-1759.