Hi webkurimaslt,
Thanks for sharing details.
You are Custom Single Product layout, please edit it https://prnt.sc/bJ4kPMHptIc7
and you can change settings of Related Product’s images size https://prnt.sc/cYOq9wTHkK_Z
In general, our theme doesn’t have such settings to adjust the sizes of images because that functionality comes from WooCommerce by default so I suggest using the default features from WooCommerce to adjust them.
Otherwise, you need to upload images with the same sizes to fix that issue. https://www.businessbloomer.com/woocommerce-single-product-image/
Please find the options on how to configure the images here: https://xtemos.com/docs/woodmart/faq-guides/image-size-content-alignment-product-grid/
Regards,