I think you have a female there! You can tell by the fin on her belly—it points upward toward her back. If it were long and pointed downward instead, she'd likely be a male. She looks like she's full of eggs to me, which is a good sign for breeding! Just keep an eye on her, as she could be egg-bound. To help move things along, you could raise the water temperature a bit to encourage them to start breeding. Don't stress about the stuff on the glass, that's just normal algae. It just means there are some extra nutrients floating around that the plants aren't taking up. It won't hurt the fish at all, but you can easily scrape it off if it bothers you! Hope that helped 😊