How to show a single image from Gallery in Twenty theme?

I am using a standard theme – actually Seventeen, but every single one after Twelve gives me the same headache.

I have established a gallery with a number of photos.
The presentation of the gallery is OK – but if you click on a specific image, the site leaves the theme and simply displays the image. I would like the image viewing to be within the theme.

It is important that my visitors can comment on the pictures.

The gallery is created in WP’s default image tool both in post and pages, the gallery is inserted as this example: [gallery ids = "162,163,164"]

I want the images to be shown on by one with a possibility of navigating back and forth between the images in the gallery.

How do I do it?

The page I need help with: [log in to see the link]