Upon reaching the central laboratory, you'll likely face a more sificant challenge, possibly a mini-boss mutant or a group of elite hostile stalkers. Utilize grenades and environmental hazards to your advantage. Once the area is clear, locate the mainframe terminal. Interacting with it will initiate a data transfer, which may take a short amount of time.
During the data transfer, be prepared for an ambush. Reinforcements, either mutants or stalkers, will often converge on your position. Set up defensive positions, use cover, and prioritize targets. After the data transfer is complete, you'll need to extract from the facility. The path out might be different from your entry point, or new threats may have appeared. Always check your map for the updated extraction route.