A common issue is the use of .jpg or .png format for images. The main problem with this file type is the lack of compression and the shear size of file you are trying to push out to a viewer.

A much better file type is .webp. The quality is the same and it is a smaller file size and can be compressed so it can be delivered to the web viewer much quicker.

Depending on how many images your website has modifying them can take some time to do but is well worth the time.

Just download GIMP.  Once installed go ahead & open > Go to File > Open to open the image you want to convert. Once the file is open Go File > Export As > Select Folder to Save to > name image as you like .webp > Next Select Image Quality (default is quite good. You’re done.

You could also open your image folder and right click & pick open with and select Gimp, then follow the same as above.