I do not know what the exact name of my profession is?

At the moment I'm doing an internship at the Fachoberschule, working in a computer shop and need an exact job description for my internship work. In the shop, we repair PC's, notebooks, printers, cell phones, etc., but also sell things like computer accessories, printers, or computers built by us. We do it all in our workshop so nothing is sent in for repair anywhere and it's both hardware and software.

There's no job title. IT system electronics or IT systems systems integration could fit quite well. Maybe PC technicians (which I think is not a proper job title)

https://www.ausbildung.de/berufe/informationselektroniker-geraete-und-systeme/

One of these professions might fit - most likely the first (see corresponding professional portraits)

IT systems engineer:

https://www.br.de/fernsehen/ard-alpha/sendungen/ich-machs/im-systemelektroniker-100.html

IT specialist (system integration).

https://www.br.de/fernsehen/ard-alpha/sendungen/ich-machs/im-fachinformatiker-ich-machs100.html

Electronics technician for devices and systems:

https://www.br.de/fernsehen/ard-alpha/sendungen/ich-machs/elektroniker-geraete-systeme104.html

Electronics engineer for information and communication technology:

https://www.br.de/fernsehen/ard-alpha/sendungen/ich-machs/elektroniker-fuer-informations-und-telekommunikationstechnik-100.html