Show only summary of posts in categories page

After purchasing the theme, I noticed that in the category pages are displayed the full content of each post and not just the summary of the posts. I would like to know how I can display only the summary of each post on the category pages.

Taking the opportunity, I would like to suggest to developers that adding the configuration to the pages of files, would be interesting, since that would be an additional point in the SEO of the site.

Note: I do not speak English, I’m using a translator.