Regretfully, there is no option to disable the theme's image sizes. It would require custom development which is outside the scope of our support. I'd also not recommend that you customize because removing the image sizes is not the only customization you will need to do. You will also change parts of the theme that uses a specific image size based on the settings in Theme Options.
To save some storage space, I'd recommend that you compress your images instead. For more details about Image Compression, please read our Performance guide at https://theme.co/apex/forum/t/customizations-performance/210.
I'd also kindly request that you do not mix topics in a thread. This often leads to confusion not only to us, the support staff but to other users as well. This results in a longer or slower response time and difficulty for other users to find answers.