lubwak: I find this white spot on the radar. I fly to it, it is pretty close. It turns out that I can fly through it too :/ I target it, shoot it, but it is like a hologram. It shouldn't be that way, right?
It should and it is. There's nothing wrong, if you can fly through a buoy.
lubwak: Well, the problem is that I can't move on! The only marked spot is this very first buoy or w.e it is. It doesn't switch to any other mark, regardless of anything I do.
When you start the mission, there's the starting buoy.
1. Fly past that, and a new blinking dot will appear on THE RADAR. Fly towards it directly, and once you reach it, fly past it. Directly. Don't try to pull any epic Heimlich maneuvers or something. Directly. Another blinking dot will appear on the radar. Repeat the steps, until you reach Snipes and his friends. Then do what you're told to do.
lubwak: Unfortunately, it doesn't show any other, just the first one. I think there was some error during installation, because the buoy appears as if textureless, almost transparent.
With Freespace open, I stopped at some mission only because one of the ship models would not load. I suspect there as be something very wrong with the installer :(
I suspect you've failed at some point during installation. I'd advise you to visit Hard Light Productions, and particularly the FreeSpace & FreeSpace Open Support forum they have there. There are many, many, many more people there who can help you compared to these GOG forums. (Nothing personal, GOG people).