First create a local folder to save all your images, then use an online tool to compress the file size ideally you are aiming @ under 100kb but that also depends on the picture content like blue sky images sometimes won’t work @ 100kb so you will have to go bigger on the file size.

Now the other thing to consider is the image width/height very big like 2400x2400px – now by resizing the image to say 1280 x 800px you will reduced the overall file kb size. Then compress image.

Tip: name your images “subject name size” eg: (two cats looking down from a tree {acf_options_contact_company_name} 600.jpg) / this helps you find images in the media library and helps tell search robots about your image and page