WP Gutenberg – custom block with two content fields

You don’t need propstwo. It doesn’t serve any purpose. There’s only one props argument, and you use it to get access to your block’s attributes. Both header and content are attributes, so you access both of them through the same props argument:

wp.blocks.registerBlockType('myblock/question-block', {
    title: 'Blok Pytan',
    icon: 'dashicons-welcome-write-blog',
    category: 'common',
    attributes: {
        header: {
            type: 'string'
        },
        content: {
            type: 'string'
        }
    },
    edit: function(props) {
        function updateheader(event) {
            props.setAttributes({
                header: event.target.value
            })
        }
        function updatecontent(event) {
            props.setAttributes({
                content: event.target.value
            })
        }
        return wp.element.createElement(
            "div",
            null,
            wp.element.createElement(
                "h2",
                null,
                "Nagłówek tekstu"
            ),
            wp.element.createElement(
                "input",
                {
                    type: "text",
                    value: props.attributes.header,
                    onChange: updateheader
                }
            ),
            wp.element.createElement(
                "p",
                null,
                "Rozwijany tekst"
            ),
            wp.element.createElement(
                "input",
                {
                    type: "text",
                    value: props.attributes.content,
                    onChange: updatecontent
                }
            ),
        ),
    },
    save: function(props) {
        return wp.element.createElement(
            "div",
            {
                className: "accodrion",
            },
            wp.element.createElement(
                "h2", {
                    className: "accodrdion-header"
                },
                props.attributes.header
            ),
            wp.element.createElement(
                "p", {
                    className: "panel"
                },
                props.attributes.content
            )
        )
    }
})

You also hadn’t correctly nested the child elements in your edit function, which I’ve also corrected above.