This is the most difficult dungeon ... I don't know how to tell you correctly ... Record every transition to the portal and see where you get, try to switch the levers and enter the portal again ... Only through trial and error can you figure out this dungeon ...
Deal with the problems of Ozersk and you can get to the Shore of Broken Ships. The rest of the questions will be solved by themselves ... In the location with lava, leave the stones in all suspicious places ...
in some places, stones should not be thrown, but simply placed in front of you ...