after the level where you have to diffuse a bomb on an oil rig it tells you to use a truck to ram the gates to a factory (I think) but when you get to the truck theres a huge gate in the way and you ant jump over, even from a rock to the right of it. So please tell me how to get past

You missed the truck... it's sorta back at the beginning.....

theres a part where it says "use the truck to ram open the gates" (or sumfin) then it means that there is no one driving the truck at that time... which means you either have killed the bloke driving it or have not gotten to it yet (man this is hard to explain).

The truck is sat at the first major camp you come to on that level... if you sneak up to it i think you can hear them talking about executing someone....

Anyway either steal that truck and ram the gates (the ones you can;t get through) or follow it and sneak in when they open the gates for it......... just restart the level