Hi Sairus! I succeded in holding the platform - the rest of the map was fairly easy . I also found out it is a good idea to start bringing all your soldiers into the tunnel to avoid early detection.
Some of my weapons were silenced. As earlier mentioned if I started shooting the bad guys in front of me, I would be spotted and the dam detonated. However, using grenades in the tunnel would not set the alarm until the stairs leading to the platform. Weird ?!
I just went through the next map also - this is really easy in comparrison. With a little luck I might finish the campaign today
Once again - thanks a lot for your help guiding me through!