Managing the style and permissions of calendar integrations

Good morning,
I want to use a calendar to embed it into my website. Until easy.

However, I would like to change the styles of the integration to match my site. For example, the color of buttons and text.
I would also like to make the calendar square, and therefore not see the Nextcloud image.

Then, I would like to modify what is displayed when we click on an event, I want to see the location, the description, but not the rest.

The last thing, I would like to make sure that I can hide the URL of my Nextcloud server. For security purposes.