Hello @Lurkaholic,
Thank you for reaching out. This issue does not relate to our theme, however, we suggest you read and follow the instructions in the articles linked below. We believe this will help you resolve your issue.
https://www.wpbeginner.com/beginners-guide/how-to-upload-large-images-in-wordpress/
https://www.freshtechtips.com/2019/03/prevent-wordpress-creating-multiple-image-sizes.html
We hope this helps.
Best Regards,
8Theme’s Team