I skipped practically all he said since I was late for something so basically dont understand what was going on.

At the end of the 'Return to sender' quest where you speak to this guy, you find out hes been doing things with the Radio, giving false information or something?
And also something about the Rangers sice he is one?
Something about the Dam?


Thats right, I have no clue what is going on and would be greatful if someone can give a quick explanation of this guys story and what he has been doing lol

He falsified a ton of reports to make it appear that the rangers had it worse than it was. This way, the NCR would send more support than required, like more medical supplies, more reinforcements, more ammo, and so on. He lied continuously because he wanted to try and prevent the death of the rangers. He thought in the end, the fight with the legion would end in failure, or at the very least, they'd take too many loses needlessly. So falsifying the reports was his solution.

Anyway, that's what I took from it.