Calculate PV rooftop potentials in Berlin QGIS 3.16. (OS Windows 10)

I want to analyse PV potentials of roofing in QGIS (v. 3.16).

I am experienced in vector data analysis but have barely worked with raster data sets. I therefore have no experience and am asking for assistance with the task.

I have access to the digital surface model of Berlin (as WMS layer) through the following link:

https://fbinter.stadt-berlin.de/fb/wms/senstadt/k_dom

I have read previous posts about similar analysis like:

Calculating total PV potential of roof using QGIS

and am wondering if someone could guide me through a similar analysis.

The SAGA toolbox that I can open in QGIS does not offer the Potential Incoming Solar Radiation algorithm.

I have further installed a SAGA standalone (version 7.8.1) that offers the toolkit.

Is there another way to calculate Potential Solar Radiation?

Side note: I have installed the following programs on my computer (OS Windows 10):

• QGIS (3.16.1.) standalone
• SAGA (3.8.1.) standalone
• WinGRASS (7.8.4) standalone
• Python (3.8.6)