Question : I changed the position of the slider! and when I upload images 1200×469 it automatically generates on images at 825×461

Answer:

The slider images dimensions for page with sidebar (what you moved on top) is set to resize all images to 825×461 in the file called general-settings.php. Change the resize rule

add_image_size(‘listing_full_slider’ , 835, 467, true);

After this you need to check old images and you must regenerate old images based on the new size rules.

For regenerate thumbs you can use this plugin: Force Regenerate Thumbnails plugin – https://wordpress.org/plugins/force-regenerate-thumbnails/