Important: cant open this path

Hi,

I want to scrape some details of this site: http://www.energieportal-sachsen.de/
If you are there, you´ll see on the left side the contents/tree. I want to learn how to scrape the following example: Click the Plus-Symbol of "Erneuerbare Energien" and afterwards the second of the four Symbols, which stands in front of "Biomasseanlagen" (it looks like an folder-symbol). Now it opens a popup with a lot of information that you also can open. Now I need to click all "plus" symbols to get the further information. And exactly these content is what I need to scrape.

My Problem: I just dont know how to open the descripted path. Which instrument of the webscraper shall i use for reaching this content?

Really thank you for your help!!