Various problems

Hello dear friend, I have installed the plugin that you recommend, I have tried it and it does not give me satisfactory results. Thumbnails come out blurry media, the menu that is horizontal makes it vertical and the footer deforms the logo.
Maybe you are doing something wrong, the sample page is as follows https://hectorfrancovig.com/pruebas/, it can be compared with the others and you can see the difference.
Thank you!

The page I need help with: [log in to see the link]