Gallery and album Thumbnail adressing mistake( only images' thumbs are visible)

Hello. I can not make visible thumbnails of albums and galleries.
I was trying to solve it, but I can’t.
However, I ve figured the source of the problem, but I don’t know how to fix it.
The problem is here:
<img class=”Thumb” alt=”Design” src=”https://i0.wp.com/design.is-more.net/wp-content/gallery/design/thumbs/thumbs_19.jpg?resize=937%2C9999“>
I don’t know why, but for albums and galleries, thumbs are resized too much. In the gallery, the thumbnail of the image looks like that:
<img title=”19″ alt=”19″ src=”https://i0.wp.com/design.is-more.net/wp-content/gallery/design/thumbs/thumbs_19.jpg?resize=100%2C75“> , so thumb apears.
How to fix this problem?

This is a link to my Nextgen gallery page- https://design.is-more.net/sketchbook/

https://www.ads-software.com/extend/plugins/nextgen-gallery/