On this page of our guide to Sniper Elite 4 you will learn where to find technical specifications that have to be stolen and how to destroy the first two rockets in the eighth mission of the game - Allagra Fortress. This guide should help you to move around the fortress.
Return to the first fork (M8,5). Now, you have to go to the second wing. Run over the catwalk and eliminate single opponents by lurking for them in the corridors and in the small room between corridors and the production hall to the East. You can use the canister by the pillar to your aid.
In the next room (M8,9), there is technical specification (M8,10) on the table, which is the first of your primary objectives. In the hall below, you will notice two rockets situated horizontally (M8,11). You have to approach them and sabotage them (without making any noise) - also, you can destroy them (with a pistol shot or a grenade that you throw from above). However, while shooting, you have to aim the front of the rocket.