Here's Venus. No, it's not a star. Yes it's closer to the sun than us. No, that does not make it impossible to see at night. That's just you not understanding the geometry of the situation. Just because the sun is below the horizon does not mean all interior planets are below the horizon as well. Mercury and Venus are always within a certain angular distance from the sun in the sky, meaning they're never directly opposite the sun in the sky but they don't need to be in order to be visible at night. I suggest you play with Celestia a bit to improve your understanding of how mercury and venus are visible at night.
[link to celestia.space (secure)]