Some people don't realize the germs that they are spreading by not washing their hands after using the restroom.
Wait for me, I'm using the restroom.
Waste is avacuated from restroom trailers by using a pump to clear the system. It's a simple process.
keep it outside!
It's his way of "Using the restroom".
It would appear that you are masturbating in the restroom. This is not particularly dangerous although it might be embarrassing if it is a public restroom. I would recommend doing that at home in your bedroom instead.
outside, if necessary. There were many public latrines in Rome for general use. Every house had some type of restroom facilities, from the built in plumbing type to the chamber pot.
They can. Their restroom may be broken, dirty or occupied.
using the restroom
Bidets are a means to clean your genitals and anal area after using the restroom.
After using the restroom or toilet room.
A transgender person should ALWAYS use the the restroom they are most comfortable using. That should be the rule. Unfortunately, some places have laws that force them to use the restroom based on their sex assigned at birth.