What experience helped Gutenberg to improve the printing process?

The experience that helped Gutenberg improve the printing press was the 1428 craftsman's revolt in Mainz. Due to the rising tensions, Gutenberg's family was forced to seek refuge in Strasbourg. Although the tensions lasted for a year and the family was allowed to move back to Mainz, Johannes decided to stay in Strasbourg. By this time, he had developed an interest in metallurgy and cutting of precious stones. It is this interest that made him start his experimentation with the printing press. Gutenberg used metal-making techniques to improve the printing procedure. He created individual alphabets made from metal components and then came up with a special ink to be used with those pieces. To print words on a piece of paper, Gutenberg dipped the letters in the special ink before pressing them against the paper. His method was fast and efficient and as a result, it enabled the mass printing of documents.
https://specialcollections.vassar.edu/exhibit-highlights/2001-2005/Incunabula/kohl.htm

https://www.thoughtco.com/johannes-gutenberg-and-the-printing-press-1991865