WordPress core gallery

Basically i’m having issues with the built in WordPress gallery:

Because Facebook instant articles don’t convert plugin correctly and offer ZERO support i have had to use the basic gallery (built in to the WP core)

This renders correctly for Facebook instant articles but sadly it looks horrible on the website ??

Is there a way to make a single image gallery but MUST be using the built in WP gallery option?

why hasn’t this been made yet lol i’m shocked.

If anyone can help me with the WP layout or tell me where im going wrong id be truly grateful