Reedalez Said:
"Is there a way to speed up iCloud photo synchronization?: Hi. I bought 200GB of iCloud storage and turned on photo syncing. My library contains 50GB of photos and videos. Synchronization is very slow (about 2 GB were downloaded in 2 hours) and is constantly interrupted. The system is updated, photo optimization is turned off, the Internet connection is uninterrupted, the phone is charged, the power saving mode is turned off."
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What's your connection-type? Cellular or WiFi?
Troubleshooting Slow WiFi:
A. Temporary Internet Files:
What happens when you clear the Temporary Internet Files from Safari? To find out how to do so, go here: Clear the History and Cookies from Safari on your iPhone, iPad - Apple Support
B. Close All Apps:
An app may me running in the background. So, close all apps. Hold you finger down as you swipe up from the bottom-left corner of your screen. Then, close all of these open apps, by swiping up quickly for each app.
C. Restart your iPhone:
Go Here: Restart your iPhone - Apple Support. Save what need be and then perform a restart. Restarting it, things would go anew.