If the manual is not listed (older versions are sometimes removed), contact Kosmos customer service. They are known to email PDFs to registered owners. Explain you need the "19er Ausgabe" (19 edition) or "Anleitung von 2019".
The Kosmos manual is copyrighted. Downloading a PDF for personal use (because you lost your original) is generally tolerated, but distributing it widely or selling it is illegal. Always try to buy a replacement manual from Kosmos first—they cost around €9.90 + shipping. kosmos chemielabor c 3000 anleitung pdf 19