If you use gallery generate by WordPress it-self or GDLR Shortcodes > Gallery, and it can’t work as it should, so we will need some customize in gallery shortcodes. You can edit the shortcodes in text mode.
The default shortcodes should look like this:
[gallery source="gdlr-core" style="slider" slider-navigation="bullet" thumbnail-size="thumbnail" link="none" size="large" ids=""]
With the default gallery, you can’t update thumbnail size or use columns.

We will need change it to look like this:
[gallery source="gdlr-core" column="3" style="grid-no-space" slider-navigation="bullet" thumbnail-size="medium" link="none" layout="carousel" size="full" ids=""]
The update in here is change the style from slider to grid, you can get more style in our document: https://support.goodlayers.com/document/shortcodes/.
