Images are the bottleneck o the web. Also for backends.
Think about to compress your images on uplaod. There are several plugisn that can do that for you in wordpress. There are also free website that can do that for you. I use “reSmush.it Image Optimizer” and dont want to miss it. It also can optize all your existing images in the media libary.
Give it a try, maybe that is solving the long laodtimes.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users