...and here is the solution. Some stuff (especially in the first section) is actually quite tricky.
(From the start in your hole) OPEN CHEST, WAIT, WAIT (Grandalf jumps through the window and drop some chocolates), GET BOX, S, DROP BOX, N, CLIMB INTO CHEST, GET DIARY, READ DIARY (there is no such date as 29/2-85, since it's not a leap year), CLIMB OUT, SET 29285, E (Grandalf asks what the treasure is worth), SAY NOTHING (a lot happens now, but you wake up in the bathroom - BEFORE the box is blown!), N, TALK GRANDALF, SAY FOLLOW ME, TALK THORNY, SAY FOLLOW ME, E (a theologist gives you a hint), NE, SAY LUX (the answer to the riddle. The trolls die!), CLIMB INTO CAULDRON, GET SWORD, CLIMB OUT, GET KEY, N, UNLOCK DOOR, OPEN DOOR, N, GET ROPE, S, S, E, E, N (wait until Grandalf has talked to Smelrond. He will give you some food), GET LUNCHEON, EAT LUNCHEON, S, E, S, S, GET CREDIT CARD, N, GET CIGARETTE, N, E, S, GET CARD, D, N, W, IN, GET SANDWICH, OUT, W, W, N, WAIT (until a crevice appears. You are captured and thrown into a dungeon)
DIG SAND (you find a trapdoor), SMASH TRAPDOOR, GET CASH, GET TORCH, EXAMINE TORCH (it ontains a battery), INSERT BATTERY (in the sword - it starts glowing), THROW ROPE (until it hits the window), PULL WINDOW (you pull the window down!), GET ROPE, SW, GET EGG, NE, SE, N, SE, E, SE, E, GET RING, DELTA 4 (suddenly you find yourself in Fergus' house), W, S, GET VODKA, GET KNIFE (no apparent use, though!), BOGGIT (to the Goblin's Gate), U, WAIT (an eagle picks you up), WAIT (it flies you onwards)
E, CLIMB INTO BOAT, DROP CREDIT CARD (you get some goods in return), GET DUTY FREE, CLIMB OUT, W, S, E, KILL BEHOLDER (with the cigarette), S, S, S, S, INSERT CARD (the door slides open), E, UNTIE DRAIN, LOOK, GET CURIOUS KEY, INSERT CARD, N, N, N, N (wait until you are captured. You are brought to a castle), WEAR RING, WAIT (till the gate opens), SW, WAIT (till the barrel is opened), CLIMB INTO BARREL, DRINK WINE, WAIT (until the barrel is opened again), CLIMB OUT, E, E, TALK LARD, GIVE DUTY FREE, GIVE CURIOUS KEY (you receive some weapons), GET BOW, GET ARROW, W, N, U, N, W, READ NOTICE, GIVE CASH (the bird tells you how to kill the dragon), NE, D, SHOOT TAIL (and so the dragon dies!), GET TREASURE, GET BARKENSTONE, S, S, S, D, S, S, W, GIVE BARKENSTONE (the ufo flies away), W, W (to part 1)
W, W, W, W, W, W, W, W, S, W, W, CLIMB INTO CHEST, DROP TREASURE (finally, you're home again. The game is solved!!)