How to make a custom category page

Here’s a plugin https://github.com/elhardoum/list-post-snippets-by-category-shortcode

Thanks! It almost works as I need it to. There are a few problems:
– It makes the featured images 250x250px big when they are 100×100
– The description is too short (4-5 words) or some posts dont have description at all
– The links to the post are not the same as the permalinks, what I mean:
if the link to my post is https://myblog.com/sample-post, when I mouseover the link to that post in that page the link is https://myblog.com/?p=43 or something like that