I will start taking lessons by next month
That is the best thing you can do.
I had a listen to your Moonlight. For 2-3 months in, you have done well. That said, this is not a good place to be starting, and the other things you have mentioned are even worse. There are some basic problems with it which could have been avoided starting with easier pieces and working up.
If you want to play any substantial amount of classical music, then learning to read sheet music is pretty much essential. It is, however, one of the things your teacher will start you off with.
As far as the "sit like this, put your hands like this" - it's going to happen. And all to the good. Your teacher will be able to see what you are doing and provide guidance much better than a description in a book can.
One of the mistakes adult beginners make is to try and rush things at the start. It's understandable in many ways, but it is much better to lay a solid foundation - and will get you playing the sort of pieces you want to play much faster (and much better) in the end.