Dear Robert,
1.) You can edit the comment form in the "comments.php" theme file. For getting more information about the comment_form function, you can visit the following Codex page.
Instead of editing the original "comments.php", I can recommend you to create a child theme.
2.) If you would like to insert a contact form shortcode into a widget area (probably using a Text widget), you will need to add the following code just before the closing ?> tag in "functions.php":
add_filter( 'widget_text', 'do_shortcode');
By default, all themes hosted at wordpress.org are allowed to use shortcodes only within the page/post content (in Visual Editor), not in the widget areas or anywhere else.
3.) To put a photo into your right sidebar, I can recommend you to install the following plugin: https://wordpress.org/plugins/black-studio-tinymce-widget/. It allows you to work with the Visual Editor also within the widget areas. For inserting a date block, you also will need to search for an appropriate plugin as this is not a core WordPress feature.
If you would like to use the background image which you can see in the theme screenshot, you can download it here: http://unsplash.com/post/71804718364/download-by-martin-wessely.
I hope that my answers will be helpful for you.
Best regards
Tomas Toman
