This is a lengthy, complex, and quite intricate mission overall. As others have suggested, once you enter the desert you must pay very careful attention to the listed objectives or risk becoming lost. Take your time, listen to Slamek. Keep an eye on your map at each stage, being certain to zoom in far enough to identify the highlighted location of the next objective, and you'll have better odds of making it through. (There's also a walkthrough available here.) Good luck!