64Gb Phone Running Out of Memory

Assuming you have iCloud Photos turned on already:

in Settings, General, iphone storage

Turn on "optimised storage "

Make sure you have enough iCloud storage and it sounds like 200GB would be the right minimum.

Manage your photo and video storage – Apple Support (UK)

50 GB iCloud may not be enough. If it is then great or, 200 is the next option.

It should do.

Just to be a bit nerdy, RAM and Storage are two separate areas of hardware, but yes you need 10% spare storage to function properly and optimise should sort that out.

You're welcome, good luck.