Here are 2 links that explain in detail [0] [1]. I'm sorry I misinformed you about Steuerbescheinigung - it's not visible there, but it is when you do Steuererklärung with smartsteuer.de.
[0] https://www.lohnsteuer-kompakt.de/fag/2020/2895/was_ist_die_...
[1] https://www.fondsclever.de/ratgeber/lexikon-investmentfonds/...