How should I describe my country's volatile situation in a letter for a scholarship application?
Something along the lines that you persisted and managed to graduate despite that the life as you know it was being destroyed in a war-torn county. The hardships of war, hunger, constant fear for safety (or whatever you feel like sharing) gave priority to the survival. As the result your grades in the final years suffered. You are eager to continue your education in the safety of whereever you are applying, and ready to give it your all without the distractions of the war.

The point you want to make is that you graduated during the whole crisis, which is truly impressive. Congratulations on that. It shows the character and persistence. Grades you can fix.