Hello Daniel,
Please follow the theme instructions here : https://doc.acmethemes.com/supermagpro/#SettingupImagessize.
Also We recommend you to use plugin named Acme Fix Image ( https://wordpress.org/plugins/acme-fix-images/ ) to crop the actual size of the images. This is also described in the theme documentation.
Hope this will solve your issue.
Best Regards,
AcmeThemes