Germany worried about one day having to fight a war on two fronts or two different borders according to the map ,was this fear justified?

Yes

Explanation:

Germany's location always put it in a critical situation: Alfred Graf von Schlieffen proposed the "Schlieffen-Plan" a strategy to avoid a two-front war reaching Paris via Belgium. Once France was defeated, full attention would be towards conquering Russia.

The French-Germann border posed an obstacle to his plan since in the early years of the WWI a stagnation of forces between them caused the initial victories to turn into a draw.

The Schlieffen Plan, proposed in 1905 was designed to make Germany the winner in the case a two-front war took place. The intention was to weaken the heavy fortifications that defended France. However, modern warfare caused many of the planned proposals to change as the new ways of fighting changed completely the face of war.