Why is downloading a title on my device slow?

Many reasons could affect your download speed. Please check the following tips to improve your speed:

Confirm your device is connected to Wi-Fi or your cellular Data and there is no interruptions.
Make sure you are not streaming or downloading any other content while downloading a title from HBO GO.
Ensure the HBO GO APP is not in the background.
Ensure you have enough memory / storage on your device.
Ensure you have enough battery life.

Tips for Android devices:

Many Android devices running on Android 5.0 and later have a battery saver solution preinstalled that kicks in when your battery is low. This reduces your device's performance and if an application goes to background mode it limits or turns off the network traffic, meaning your apps may not update and reason why your title may be slow to download.

For faster downloads on your Android device turn off the battery saver mode:

Just plug in your phone or tablet and start charging it. Android will automatically disable Battery Saver mode while charging, and it’ll stay disabled when you unplug your phone.
You can also turn off Battery Saver mode manually. Just pull down your notification shade and tap
Turn Off Battery Saver” in the “Battery saver is on” notification.
You can also visit the Battery Saver screen in settings and set the slider to “Off.”

For more info: https://support.google.com/android/answer/9079240?hl=en