Hello, everyone! I'm a lurker on this subreddit. Now to start off, let me say that I have confidence to approach girls. I don't flat out avoid them like I used to. However, I've found that most of my attempts to have conversation with them are worrisome. Here's why; most of the time my attempts at flirting are kinda insulting. Let me show you what I mean. This is a conversation I had with a girl that's new to my school (I'm a junior and she's a senior):

Me :"I haven't seen you here before; are you new?" Her:"Yeah" Me:"Where from?" Her: (city name) Me: Oh... (other conversation)

So far so good. This was the conversation where i found out she was a senior, and said she looked like a junior. She said she took it as a compliment. Then tomorrow rolls around. This conversation was shorter because in the previous situation circumstances put us together, but this time I attempted to talk to her on our way out of class:

Me:"Are you sure you're a senior? (insert whatever else was said here)" Her: "I think I would know what grade I'm in."

record scratch

Maybe I'm overreacting, but at the same time I know what it feels like to have someone talk to you that you're just always annoyed with. I just don't want to make her feel uncomfortable/frustrated.
This past 30 days I've scaled the wall of self consciousness and fear of being made a fool of. Now I have to learn how to use this confidence as a tool with women. Especially flirting. Whenever I try to flirt, I think in my head hey, it would be a pretty good idea if I said something snarky and possibly offensive. That'll work! I'd really appreciate some input. Thanks.

Tl:dr: my method of flirtation is snarky and, in my opinion, can be offensive at times... how do I flirt in an interesting yet sarcastic way that's not offensive?

Edit: reddit mobile makes my post so aesthetically revolting