Fix in Wordpress website

I own the website [login to view URL] and I make it myself. I have something that I cannot edit and maybe I need a little help from someone who knows. My problem that I need help, can be shown in the page [login to view URL] It is an updated wordpress in latest versions. In there as you can see, there is a image gallery showing the pics of my apartments. The problem is that the original pics are 2:3 but here the images are shown in 1:1 so I cannot show the pics correctly. It zooms my pics, loosing the edges. I want someone to edit the code in order to use another analogy or use my original ratio. More specifically, when i enter a foto from wordpress media library (for example a 3000x2000)... it generates several versions of the original foto... .1000X1000, 1024x683 etc... I want only to make a change by changing the code in pics gallery slide to select another version of the image and not 1000x1000 that is 1:1.... I want it to choose the 1024X683 version of my images. I have attached a screenshot also. Thank you very much