Yeah if i remember correctly you are right. But I can add that at 5 the gas chambers are basically gone, but right behind them, the big grey area we see, is a big memorial that has been build afterwards.

Also i believe the building on the left was some kind of workcamp where a few prisoners were "allowed" to help kill their fellow prisoners in some way.

Source: Was there 2020 right before the pandemic. One day Ausschwitz 1, one day Ausschwitz 2. Harrowing experience, but I can still only recommend visiting both.