For the first flashback of Reznov, just follow Petrenko and ride the vehicle. Watch the following scenes.
Objective: Assault the German base and find Steiner
Fight your way until you reach the target building. Kill the soldiers inside and head to the second floor. The intel is located inside, on top of the table in the corner. After discovering that the target is not here, follow the waypoint to the next objective.
Project Nova Intel 1/3
Exit the building then follow your comrades. You should be able to call in mortar strikes now so use them to your advantage. Fight your way through until you reach a hangar housing a V2. The next intel is located in the small room in the corner.
Project Nova Intel 2/3
Head outside and follow the path. You'll need to plow the remaining german defenses. Use your mortar rounds to kill them easily then follow the waypoints to reach Steiner.
In the next part of the mission, head inside the ship and follow the waypoints to reach the chamber containing Nova 6. Watch the following scenes, until you're able to escape.
Objective: Escape the ship detonation
Fight your way in the larger room of the ship. Make sure to take out as many as you can before arming the explosives; you only have 3 minutes to run outside and escape the blast. After arming the explosives, shoot the highlighted support beam to create a pathway for you. Make your way outside and kill anyone along the way.
Head to the end of the ship and before reaching the stairs, look on the floor to the right to find the intel.
Project Nova Intel 3/3
Zip down to escape the ship and complete the mission.