Thanks for your reply Jordan.

I just installed a new WordPress, so I can give you everything. I just made one page, and I added the gallery from the theme onto my homepage. I also put a screenshot, and I highlighted the text, so you can see what I am talking about.
Again, I cannot reorder my pictures by drag & drop. It seems, this feature should be available and it just does not work. So if you go and edit the gallery, you can see my 3 pictures, then you should click on “Add/Edit Gallery” button, and then you will see the same page that I already took a screenshot. On that page, I cannot reorder my pictures by drag and drop.

Thank you,
Looking forward to hearing from you.