Integrating LuxCal-Calendar - how to start?

I found a free web calendar (see which keeps the data on the own site (this is strictly required).
My knowledge of PHP is not existant, so I’ve no idea how to integrate this tool into a site using grav. As far as I understood the recipe on including own php-functions works for function which return one “string”. The viewing pages of the calendar (monthly, etc) don’t seem to work like this…
Next idea: using plain iframes. This works, but is not very responsive.

Any idea on how to integrate the calendar-views into a grav site would be welcome.
(e.g. Is it possible to make an iframes height responsive?)

It looks to me like you can download LuxCal and use a local sqlite database. You don’t need to use the LuxCal site. You’d need some PHP knowledge to make it all work. As for responsive iframes, Google has various thoughts on the matter.