Are you trying to learn to play classical music by reading sheets or do you just want to be able jam? In both cases, I'd suggest spending a lot of time learning music theory. A lot of the programs use pianos for a reference and could be something you use side by side, but at least a basic knowledge of music theory will help you tremendously. I took piano lessons for two years about 10 years ago but didn't remember much. I stayed active in vocal performance and theory and have always been able to sit down and play single or two lines of music without problem. Anything more complex like a lot of famous classical pieces would need a lot of practice on your own specifically at a piano. I'd still say try that after having an understanding of music theory. It will make your life so much easier and will allow you to hear things a lot better as you play. It will make much more sense.
Hey, thanks for the advice! Any tips or examples on what you mean by music theory? Is there a decent Youtube series or something like that? Just calling it music theory sounds like a very broad topic to me, and I'm sure there are people who study that on universities. So any guidance for that? To what point would it make sense for me to learn the basics and where should I draw the line?
Yes, there are definitely people who study this and can get P.h.ds in Music Theory I believe, but obviously not all of it is relevant to someone just trying to learn basic piano skills. I'd say that for making learning and playing the piano easier you should learn about chord structures and progressions, so that you can essentially "free-style" if that makes sense. You'll find that a lot of songs follow the same progressions (you've probably seen the four-chord song on YouTube). I'd also take a look at ear training so that you can have a better relative pitch (identifying what each note sounds like). I'm not sure exactly where I'd "draw the line" but honestly if you just spent a few hours with the stuff above and had some charts handy while you learned it would be helpful. As a fan of music you might find it interesting as I do and want to go further with it. There's no way that I wouldn't help you, it just might not be necessary for the level of skill you're trying to obtain. I know there's a lot of online resources that are free, but I personally haven't used any so couldn't recommend them myself. I have heard good things about teoria, but just look around to find something you like -- I'm sure there's even mobile apps for it.