Commerce 2 Add to cart with quantity field and Product Picture
Please check your order item type e.g. admin/commerce/config/order-item-types/default/edit/form-display/variation_cart_form (default type)

Needed view mode is variation cart form. There is quantity field.

Also check this default view mode for your product variation type /admin/commerce/config/product-variation-types/default/edit/display

There is add to cart button.