@sabina.balanescuWelcome to the community!
You have not provided enough information required to properly answer this question. But here is some information that might help (based on provided information).
First and foremost, yes, you can create plugins in Confluence (for both Server and Cloud version)
Secondly, to automatically update content of certain page based on changes in other page, this can be done using multiple ways,
I can be more precise if you can provide little bit more information about your hosting type and use case.
Have you considered using the Activity Stream macro? Unless you need complicated metrics, it does the job nicely provided your summary page is also in Confluence.
Apart from the answers provided, one of the following should be of help to you in re-using content across pages in Confluence:
Let me know if you meant something else.
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