What country are we talking about? If this is a fictitious place, YOU as the author control reality. If there are cultural reasons to have it be strange or different, then make it so, and make it up. If it's historic, there may not have been a restroom, but THAT would be a history SE question (so do your period homework before asking).
In the USA, at least, they are 95% identical. If you've seen a unisex bathroom, use that as an example. Women's typically has more stalls in place of urinals. You can google urinals if you really want to, and see the various styles. Sometimes there are dividers, but not often. Occasionally, there is a long trough (in sports stadiums, for example). There will be lots of searchable images. Generally, men's bathrooms are either the same overall (except for urinals) or simpler. Most of us have at some point cleaned restrooms, been dragged in as children (if you remember that far back) or just seen the other gender's restrooms when they were open for cleaning. I can't speak for other countries, but if you're really curious, ASK someone from wherever what it's like. After the weird looks, tell them you're an author trying to accurately portray a setting, and unless there are serious taboos, they'll tell you.
Most of the time, it isn't relevant. As fun as potty humor can be (and I work in a hospital lab testing EVERYTHING, so the bad jokes are pretty thick), there is rarely a call for it unless a scene happens in a bathroom. It is rare that a reader wants that level of detail.
- PS your friend may be ripping on you for fun.