This is the movie that goes with Werner Herzog's director's commentary track on Fitzcarraldo.
Werner plays himself as a crazed film maker, willing to risk life and limb (others' as much as his own) to get those special effects only obtainable if you do them for real. Tribal politics play a role, as the presence of indigenous Germans leads many to expect the worst and/or want a piece of the action.
Werner monologues about his existential problems with the Jungle's decadent opulence, plus shows a crazed Kinski losing it with the crew (bonus feature). Also in the bonus features, Werner eats his own shoe, for reasons unrelated to the making of this film.
For those skeptics and cynics who don't think this all really happened as portrayed, check out the clip from the first version (before the restart) featuring Robards and Jagger, as the split personality earlier cast for this role, and filled handsomely by Kinski once the film ran into problems (probably mostly around Werner's ego, though no one ever comes right out and say so on the director's cut).
This "making of" spends a lot more time on the rubber making process, rubber barons, and their love of opera, being so pivotal in the more fictive version.