Pics Clear on Computer, Blurry Once Uploaded to Media Folder

I’m new to WP and I’ve spent nearly 15 hours trying to figure out why this is happening. It doesn’t matter whether the jpegs are resized to 100 kB or 1 mb original photos, once I upload them to my media folder, most are blurry as if I had resized them using a quality of 30. It doesn’t seem to happen to every photo but happens to most.

Is there a setting somewhere I can change, a special way of uploading or some other trick to prevent this from happening? Thanks for your help. ??