1. Create a child theme
Download a ready-made child theme for Neve – and install it as a new theme.
vgl. auch: WordPress: Neve: Create Child Theme
2. Change the default image size
Add the appropriate code snippet at the end of the functions.php file of the child theme.
function change_blog_image_size() {
remove_image_size( 'neve-blog' );
add_image_size( 'neve-blog', 420, 220, true );
add_action( 'after_setup_theme', 'change_blog_image_size', 100 );
The value of 420 is the image width in pixels and the value of 220 is the image height in pixels.
3. Source:
https://docs.themeisle.com/article/1269-how-to-change-image-size-in-neve