I want to save(download) images in my device…


If you mean pre-downloading images so they show up when you are reading while offline, head to the Preferences menu and enable Download Stories and Download Images and you’ll be good to go.

If you want to save an image from a story, you can long-press on it and select Open Image, which will open it in your default web browser, from where you can manipulate it however you like.

I can not long press on it some story’s images and text mode.

Ah, that happens if the feed isn’t properly setting metadata on all of their images.  For feeds that aren’t up to snuff, it is probably best to open the story in your browser (tap the story title) and work from there.