As a general guide you can resize your images into big, medium and smaller. If your biggest images will be limited by the width of the site page, then use 1200px. For images that may fill a column use 800px. Images that don’t fill their container edge to edge could be resized to 300px. Note that a 800px image is not that much bigger in file size than a 600px image.
If your images are jpg, then the very best way to resize, create multiple sizes and optimise is to use jpegMiniPro which you could setup and drag all 293 images into and it will do everything. Using Photoshop to do this to 293 images could take forever.
Alternatively the free jpegMini will do up to a limit of 20 images per day - at least that’s how it used to work.
If you have a mix of png and jpg images you could use one of the many resize apps such as Super Resize to resize and then drop all images into the free imageOptim to optimise both png and jpg images.
BTW that 1.8mb image is way too big. Ideally aim for nothing bigger than about 300kb for the biggest image on any page.