Hi @ollo, I am no Google Calendar expert, but there is options for customization, from that page:
"If you'd like to customize your embedded calendar, click the Customize the color, size, and other options link above the iframe field to access the Google Embeddable Calendar Helper. Carefully select your options in the Calendar Helper and paste the customized iframe code in your website."
Now, if that still does not work, you can experiment with custom CSS to alter the look of your calendar, this is custom code, so you need to work with this yourself or get some help on the forum from some of the nice folks here
Another option entirely is to use some other calendar scripts, which are also custom code, but it is possible to use a jQuery plugin for example to make an appointment calendar, you have to look around on the net for such plugins.
I wish we had a Calendar widget right now, that can help you, built in to Webflow, but we will need to wait for that in a future update.
I hope that helps ! Let us know if more questions. Cheers, Dave