So I requested a takedown for a picture I uploaded here by mistake. They gave me a verification code and told me to speak to DragonfruitPrints on his social media accounts. I've send the code to him on his Twitter, FurAffinity and Deviantart account. I got no answer.

I also tried flagging the post. I flagged it two days ago, and I was told the picture would be removed within 48 hours. Nothing happened, the picture was unflagged for some reason.

So what do I do? Do I have to wait for DragonfruitPrints to answer me or is there a new way of deleting my posts?

The takedown was only made 10 hours ago. Only one person handles takedowns and they can't be awake 24/7, please give it at least a day or two.

In this case you can simply upload your new version and flag the old one as inferior, as that would be the correct flag reason. There's no need for takedowns to do that.