How did Germany react to having their territories taken away from them after WW1?
Generally speaking, Germany reacted to the loss of their territory with anger and with a determination to regain those territories. This is part of what made Germany so upset with the Treaty of Versailles and so determined to break out of the constraints set by that treaty.
Germans felt that they had been abused by the peace process that happened after WWI. They felt that the taking of their territory (among other things) was extremely unfair. Because their territory had been taken, they wanted to regain the territory and to restore their former power and prestige. This is part of what got Hitler into power later on. He promised to help accomplish these goals for Germany.
So, Germany's reaction was an angry one -- one that was aimed at regaining the territories. This reaction ended up helping to cause WWII.