Thumbnail images being cropped in portfolio overview

Hi,

On the portfolio overview page that I try to customize, the thumbnail image is cropped. How do I change that?

Have tried to change the thumbnail size in the wp admin (settings/media) but that didn’t help. Have also tried to change widht and/or height settings in child css for:

#content-archive .has-post-thumbnail
#content-archive .has-post-thumbnail img

but that didn’t help either.

Would very much appreciate help in this matter.

Best regards
Cecilia