Always looking for something in this game,does some know where are exict some video lessons for exactly
finding water purifying chip or finding invisible caravan, etc..what kind of weapon using against mutants,
may i buy time or how can i come inside brotherhood base ?


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Not sure about the videos, but you can find lots of information/walkthroughs/hints here:

http://www.gamefaqs.com/computer/doswin/game/197289.html

If you want videos, just check out YouTube http://www.youtube.com
And type in Fallout and whatever your looking for like "WaterChip"

And yes you can extend the time limit, by doing certain things in the game! I would say but I don't wanna create any spoilers! PM me if you want to know!

If you really must spoil anything for yourself, then just find the location of the water chip, because after that you only have to worry about finishing the game within 13 years.