Hello there! Through the Treaty of Versailles, Germany lost a lot of land including the following:
• Lorraine
• Alsace
• Czechoslovakia
•Malmedy
• West Prussia
There were lots of other territories Europe lost, and more notably, that was known as all the oversea colonies in China to the Allied Nations (The U.S., Britain, etc). The Germans were forced to cede territories to Denmark and Poland, too. That is over 10%! Hope this helps!