Are you saying that for a single gallery with, say 50 pictures, I would actually have to upload one picture at a time? Seriously?

Isn’t a “featured image” the picture associated with the gallery and not the actual pictures in the gallery?

Are you saying that every picture in your galley is a POST? So for a gallery with 50 images, there will be 50 posts? REALLY?

I must be misunderstanding you. Please explain:

What would I do to create a gallery with 50 pictures?