Weapons Captured from Czechoslovakia, Poland, Finland, Italy, and Central Europe
The German army was exceedingly frugal when it came to equipping troops with firearms and other equipment. Huge stores of foreign war material were captured as countries were annexed, conquered, or as enemy troops were defeated. Some of these weapons were reissued to German soldiers as substitute standards. With the conquest of the annexation of Czechoslovakia and the conquest of Poland, many thousands of Central European guns became part of the German Arsenal. Even more importantly, all the highly valuable Czech weapons manufacturing centers became part of the Greater German Reich and continued to produce arms for the duration of the war. Czech factories were often retooled to produce weapons in German configuration such as the Kar98k while other factories continued to produce Czech configured arms for the German armies. In addition to the continued production, there were enormous quantities of arms absorbed from Czechoslovakia, captured from Poland, and taken from former allies such as Finland or Italy when they switched sides. Czech Machine guns such as the ZB26/30 and the ZB37 were used heavily by the German army.
In the case of these photos, it is impossible to tell without more context if the soldiers were issued these guns, using them without orders, posing with them as curiosities, collecting them for disposal, or anything else. We cannot merely assume that the fact that we see a soldier holding a foreign gun the German soldier pictures was actually issued it or even using it for any prolonged period of time.