Your image is currently 768×1152 px, which is a portrait (vertical) format.
If you need it resized to a different aspect ratio (for example, a landscape format like 1500×500px), it’s unfortunately not possible without either cropping or stretching the image.
One smart workaround — if you have Photoshop — is to expand the canvas to your desired size and use Content-Aware Fill to let Photoshop generate extra background on the sides. This works particularly well with soft, natural scenes like this one.
If you're only scaling down and keeping the same proportions, then you can safely do that in any basic image editor without distortion.