@kmelvin this is because the theme is set to crop the images to fit the predetermined sizes for thumbnails and other versions of the featured image.
I assume you are talking about the image thumbnails on the front page under the “Latest news” section. You might be having issues because thaat thumbnail is set to be a perfect square, so if your images have a different aspect ratio, they will be cropped and not resized keeping your original aspect ratio. To change this go to functions.php in the theme directory and find
add_image_size('post-thumbnail', 250, 250, true);
Leave the first 250 (width) and correct the 250 to reflect your desired aspect ratio. This worked well for me, hope it helps! In that same section, you can change the way the theme crops images for different devices, make sure you check out what measurements work for you.
To keep in mind for the future, it would be a good idea to have your featured images always have the same dimensions.