What role did the Eastern Front play in the campaigns of 1914, 1915, 1916?

The order is:

In 1914, on the Eastern Front, they succeeded in conducting a successful offensive in Galicia (August-September) and defeating almost half of the Austrian regular army and occupying Lviv, and at the same time helping Serbia in defeating the Austrians near Belgrade. The operation in East Prussia was unsuccessful, but the Germans transferred some divisions there from France and lost the battle on the Marne.
In 1915, the Eastern Front diverted most of the German and Austrian armies, but it cost huge losses and retreat to the Riga-Baranovichi-Ternopil line.
In 1916, on the Eastern Front, a successful summer offensive was carried out on the southwestern front and caused great damage to the Austrian army (the Germans suffered less).