One of twelve children, Gajewski only had limited schooling due to his family's lack of money but, following the completion of an apprenticeship as a pharmacist, he was able to enrol in the University of Leipzig in 1905 to study chemistry and pharmacy.

[1] He was recalled to manage the BASF gas works at Ludwigshafen-Oppau and around this time he married Elisabeth Seckler, eventually fathering two daughters.

Gerhard Ollendorf, a Jew, had been a member of the board in the early 1930s but had fallen afoul of Nazi laws and in November 1938 told Gajewski that he intended to leave Germany.

[2] His role as a member of the company's South-East Europe Committee, a post he took up in 1940, made him a regular visitor to IG Farben sites that had been established in occupied and satellite territories such as Hungary, Czechoslovakia, and Romania.

[2] He returned to the business world with Dynamit Nobel, becoming chairman of the company in 1952 and was awarded the Großes Verdienstkreuz the following year by the West German government.