Hi there,
Some of the CSS with the !important in their properties are baked into the woocommerce stylesheet file of the GP premium plugin but you still should be able to override this by adding !important AND being more specific on the selectors.
Example:
tr.woocommerce-cart-form__cart-item.cart_item td.product-remove a.remove {
color: #e5e4e2 !important;
background: green !important;
}
tr.woocommerce-cart-form__cart-item.cart_item td.product-remove a.remove:hover{
color: blue !important;
background: pink !important;
}
Adjust its values to your preference.