Some downloaded images look blurry and have a tiled effect. Why is this and how can I correct it?

Question

It's as if the resolution is wrong and they appear to be enlarged too much.

Answer 1

If an image has been upscaled, you can't modify it to bring the picture to an acceptable resolution because it's not possible no matter the editor or technique used. You can try that by yourself: take a small picture and enlarge it enough then try to bring it to quality you like. You will see that it's not possible.