Gutenberg: unable to save attributes with ServerRender

I got a result after 4 hours of stupid try & error

I’m unable to read values from source meta in the frontend.
I assigned the variable from meta to a regular string attribute and it works. Easy Peasy.

/**
 * BLOCK: bold-blocks
 *
 * Registering a basic block with Gutenberg.
 * Simple block, renders and saves the same content without any interactivity.
 */

//  Import CSS.
import './style.scss';
import './editor.scss';

const {__} = wp.i18n; // Import __() from wp.i18n
const {registerBlockType} = wp.blocks; // Import registerBlockType() from wp.blocks
const {ServerSideRender} = wp.components;
const {AlignmentToolbar, BlockControls, InspectorControls,} = wp.editor;

const {
    PanelBody,
    PanelRow,
    Fragment
} = wp.element;


registerBlockType('cgb/block-bold-blocks', {
    // Block name. Block names must be string that contains a namespace prefix. Example: my-plugin/my-custom-block.
    title: __('bold-blocks - Example Meta Content'), // Block title.
    icon: 'shield', // Block icon from Dashicons → https://developer.wordpress.org/resource/dashicons/.
    category: 'common', // Block category — Group blocks together based on common traits E.g. common, formatting, layout widgets, embed.
    keywords: [
        __('bold-blocks — CGB Block'),
        __('CGB Example'),
        __('create-guten-block'),
    ],

    attributes: {
        metaToDisplay: {
            type: 'string',
            source: 'meta',
            meta: 'werk',

        },
        className: {
            type: 'string',
            default: 'fuck'
        },
        werkId: {
            type: 'string',
            value: 'foo',
            default: 'shit'
        }


    },
    edit(props) {
    //    const {attributes: {metaToDisplay, className}, setAttributes, isSelected} = props;

        let metaToDisplay = props.attributes.metaToDisplay;
        let className = props.className;
        props.setAttributes( { werkId: metaToDisplay } );
        props.werkId = props.metaToDisplay;


        return (
            <ServerSideRender
                block="cgb/block-bold-blocks"
                attributes={{
                    metaToDisplay: metaToDisplay,
                    className: className,
                    werkId: metaToDisplay
                }}

            />

        )
            ;

    },


    save: function (props) {
      //  const {attributes: {metaToDisplay, className}, setAttributes} = props;
        // Rendering in PHP
        return null;

    },
});

I’m sure, that I’m doing some kind of cargo cult here. Can somebody provide me a more elegant solution for my problem?