I didn’t realize that the excerpt existed because I have posts instead of pages. I installed a plugin to correct it, so now it’s done! Thank you very much!!
About the other question, I realized that if I set the columns option, I have problems with the customization I did for another pages (for example the no-results page). So I tried to set the blog page with no columns, but putting the featured image in the left of the header and the excerpt, instead of above or below the header, but it doesn’t work, maybe I’m doing it wrong. How can I do that?
Thank you so so much for your help.