I talk to him but then after that i can't go in through the door help me!
Watch for the "clues" to open doors, etc. There are two bosses you fight, and they give you the clues to open the doors.
1. Fight Firegut. Get first combination (sun, bird, tree, beetle). Go back to Watson and open first door. (This will stay open as long as you don't leave the dungeon.) To open the door, there are 4 plaques hanging on the walls alongside the first door. (NOTE: They are very hard to see on my computer. I have to walk right up to each one to see what image is on each plaque.) Press "x" in front of each plaque following the first combination you just got.
2. Second door is locked. Watson says to go fight Clanker. Get the SECOND combination from Clanker. Return to Watson. He says to open the second door. Use the 4 plaques again, with the SECOND combination from Clanker (tree, sun, bird, beetle).
After you open the second door, it stays open as long as you don't leave the dungeon.
Hope this helps.
*Edit: note to moderators* Oops. I think I goofed. I'm not sure this is the right quest. Please delete my reply. Thank you.