I created my first wordpress plugin now. There are probably some things wrong or not done with best practice. But if anyone can use it, please go ahead. You can also fork or create changes on github if you like. It’s located here:

https://github.com/fwermelinger/wppizza_openingtime_shortcode

I’ll update it a little bit as soon as I have time. First things to do will be:
– add the actual link to the settings under ‘WPPizza’. (It’s now under the general WP-Settings)
– Create another option to set it as a countdown. We had that before. Something like (We will open again in: 6 hours 28 minutes)

Regards,
Florian