Featured images wrong display

Hi,

Last week I added two posts and inserted featured images without having trouble.

However this week I haven’t manage to do it. The featured image is shown in a big size elongated. I have tried to scale it, crop it, but I can’t manage to find the size that would fit.

I think this happens because I have updated my wordpress version and some plugins. At least this is what I think as I don’t see why last week it worked uploading a featured image very easily (just as a normal photo) without resizing, scaling or croping the image.

My website is: https://youthandmuseums.org/alumnus/

Thank you for your help!