featured image size

Hello,

I have been getting to know the newspaper theme recently, and I’m having a few problems with my images. Each time I optimize my image to under 2500 px which it says is recommended and under 2 MB my photos are not uploading. I seem to get a notification to say “post-processing of the image failed likely because the server is busy or does not have enough resources. Uploading a smaller image my help. suggested maximum size is 2500 pixels” Therefore, I resized my image to 800 x 400 px and it let me upload it, however when I use those pixels on my large images and I refresh my website to view the image, it is really blurry and does not look good quality.

Hope you can help

Thank you