Stop entries appearing twice?

Hmm, you have a widget first, and then the normal shortcode. That is a bit strange :).

There are shortcodes that will show just the form or just the entry-list:
Instead of the ‘[gwolle_gb]’ shortcode, you can use ‘[gwolle_gb_write]’ for just the form, and ‘[gwolle_gb_read]’ for the list of entries.

Using that shortcode would give some more control over the list compared to the widget that has less controls.

Thanks Marcel for replying swiftly.
Using ‘[gwolle_gb_write]’ solved the problem!

Am using TESSERACT theme with Page Builder in second row: Have put
‘Gwolle Guestbook’ widget, above Visual Editor containing [gwolle_gb_write].

Looks good to me!