Cannot redeclare myScreenshot()

By activating the Plugin I’ve got a fatal error:
Fatal error: Cannot redeclare myScreenshot() (previously declared in /homepages/37/website_id/htdocs/websitespace/site/wp-content/themes/canvas-childtheme/functions.php:813) in /homepages/37/website_id/htdocs/websitespace/site/wp-content/plugins/wp-screenshot/wp-screenshot.php on line 16

Where should I search the problem or is there a problem with the code?

Thanks for helping.
Best regards,
Mat

https://ww.wp.xz.cn/plugins/wp-screenshot/