Hi I'm developing a game that's gonna have a lot of secret passages it's on a secret passages and a mansion now how do I set up the room to go into a secret passage but cannot go back in the opposite direction?

When you make a passage, or exit, uncheck the "Also create exit in the other direction".
Now, you have a one way exit.

Or if exit already there delete the exit the other way. Simples

You can have exit close by making a script that runs every time you "enter the secret passage room", effectively closing the exit behind you as you enter. However, if you want to open it again, you need a lever or other thing to open exit when already inside that room, otherwise every time you enter that room it will close or lock that exit. So being already in that room and activating exit to open will work fine.