Windows Phone 7.x is no longer supported by Microsoft. The store is now incompatible with Windows Phone 7.x apps. So you can't download any more.
As of today, also, Microsoft has ended push notifications for WP 7.x and 8.0 phones.
https://www.theverge.com/2018/2/19/17027562/microsoft-windows-phone-push-notifications
Your best solution is to change phones to a newer device running Win10 mobile or switch to Android or iOS.