Slow browsing photos with android app

Browsing photos in gallery is slow. Each new pictures have to be downloaded (!) separately before you can view it and even when they are synced and stored on local device it sometimes take seconds for the pictures to be shown !!
I am using LTE and samsung Galaxy S5neo (not newest device but generally works fine). Size of pictures about 3-4MB.
I can’t unterstand this because they only have to be loaded from local memory - browsing pictures or photos stored locally with other apps (like file explorer and others) works very fast.
Again (sorry !) Cirrus- app seems to do this much more effective (pictures and photos do not have to be synced or downloaded before they can be viewed) - nevertheless they are shown relatively fast !
Any Idea ?
Kind Regards, Joe7

Well known issue and in progress on a fix. Closing as per PM conversation