Wordpress image sizes all wrong

Apr 8, 2018
Hi guys
using a free wordpress theme that seemed to work fine for a while.
But now, lets say I download an image 500 x500 pixels to my media library, the actual size shown is 271 x 186 which is useless to me.
I don't want to use Canva to resize it as I find that distorts too much.
I have gone into setting and changed the thumbnail sizes to 300 x 300 and the other sizes larger but I still keep getting the problem.
Can anyone help please?