I guess you have figured out the files are in one of the labs ("The Archives"), so the first question is which lab is it? Next is how to get in without getting noticed. Not getting into too many details you can lure the scientists out of the lab and sneak in, or make someone escort you into the lab. Try talking to people in the base, both outside and inside buildings.

I did just that but neither option solves the mission, if I speek with the three soldiers one of them can get me in the archives but heike is a strong independent frigid woman which then gives me an option to kill him or let him go. either way I dont get enough time to gather enough and get out. than there is that mechanic which have two choices but neither of them gets me anywhere, the leader in the bunker to whom I gave some papers but that did nothing and some talk in the warehouse that just gives me some info. Everyone else either sends me out or calls the guards. so how can I get the scientists out?

All right you really have been all around :P You will need some sort of diversion. If there is already shooting and chaos then who is gonna notice another shot? And if you plan to sneak in on your own without help, you just need to distract the scientists in the lab or lure them out. After all, they tend to swarm whenever someone is hurt.

Well, I just attacked the Russian base with the rest of the soldiers. All the camp went to push them back and I had plenty of time to gather tons of documents.

Hello,
I dunno how to complete this one tbh, I restarted it like 30 time, can't managed to distract the dudes. I got the intel, but can't get out of the lab, there is all the base waiting for me...
Any chance someone show me the way to do it ?

This will sound awkward, but I don't know how to even get into the russian base without getting a game over. I always capture the supply truck and put Heike in it, but when I drive in and the guards ask me the questions, it ALWAYS results in a game over. How do I answer the questions correctly? Or rather, is there a way to get in without the truck?

There are three options in the query when entering in a cargo bay. One is always false; which one of the other is true depends on the direction from which the cargo bay entered the map. In the very first line of dialogue in the mission Dwayne indirectly informs that A. I. Yegorov is to the west and Y. E. Yakir is to the east.

Sorry, but really stupid mission. I get the truck, but all the times I go with it to the base, the guard say: Enemies! And I am totally lost. No way to infiltrate the base. Base is to strong to infiltrate with tactics.

I hate, when the game cheats and this is that, what the game in this mission do. In the northeast base is barracks, which I destroy with 4 stolen vehicles and enemy build new barracks still again and again. On the west side, I tried to destroy some building with the bombs, but the game is still cheating. No way to done it. Sorry, I really liked the campaign, but this mission is really stupid and has no Original War soul.