You really need to call a plumber.

It's not very clear what you're trying to accomplish. And the photos are pretty tough to sort out what's going on. I don't see any venting for any of the current fixtures - is that what you are fixing? Are you planning to convert the 1.5 to 2" for the shower?

Sorry for the crappy quality photo. Basically im wet venting the bathroom. The vent is coming up through the floor where i circled. That pipe is 2”. My sink is going to tie into that. After my sink ties in can i reduce the 2” to 1.5” for the vent portion that will tie into the stack?

Thanks for the answer. I realize a big one is having the shower at 1.5” i think alot of places its 2”. But over here all this passed inspection. Hoping i can find a codebook somewhere. I cant justify paying someone over 200$ just to tell me i need to make the vent 1.5” or 2”.

My code books are in storage, but venting 2 fixtures with 1 1 /2" pipe shouldn't be a problem.