How can I test if I am at a page or a post (php if-test)?

I can’t see the ratings anywhere – but maybe you disabled the plugin.
Now, the easiest way is to create a page.php template file (that doesn’t have the code for rating), WP will use it automatically for displaying your Pages.
See:
https://codex.www.ads-software.com/Pages (and the Templates section)
also:
https://codex.www.ads-software.com/Template_Hierarchy

However, if you want to go with one file (index) check out this:
https://codex.www.ads-software.com/Conditional_Tags

I fixed it, thanks for the link to the codex. I’ve been reading up on it this passed week.

the test I run is this:

is_page()

It will return true if the page is indeed a page…

Check out the results on https://www.torkiljohnsen.com/hattrick

You will see that the About page is without a rating now ??