YouTube is fastest, learn everything there ez, also can learn how to make crack cocaine and heroine (analogy)
If you have money pay for a teacher
learning sheet music isnt that difficult, but the only way to be good at it is to gain familiarity with it, which takes practice
also, learning proper technique using only an app as opposed to a teacher is gonna be really difficult.
i started taking lessons when i was 5, and honest to god i dont think i wouldve tried to learn this song until i was abt 7ish. piano is a lot more complicated than it seems, not really something you can pick up over night
One word, practice. Getting a teacher will likely be the fastest way as they'll be able to help you make the most of your practice time, guide you on what/how to practice, and help get rid of bad habits/technique early.
I learned everything by going to a secondary school (music) parallel with elementary school. Started out with 1 year solfege, where I learned how to read and write notes in treble and bass clef. After a year, I started with piano lessons as well where I played very easy tunes, learning about rhythm, dynamics, articulation, finger placement and just the essentials (right hand only / left hand only). After you get comfortable with playing both hands individually, you star to play them together, while simultaneously working on everything mentioned above. From this step onwards you need time, patience, determination and hardwork. If you are an absolute beginner and aren't planning on getting a teacher, find anything you can on the internet about which note is which on both paper and on the piano. Search up for some of the easiest tunes online, watch as many tutorials as you can and start practicing. If you are determined, you can play some of the hardest pieces of music in 5-10 years.
I myself am playing for about 10 years and have been to many regional, national and international contests where I've won many awards. Although I stopped playing piano (I am a drummer now) I am very proud of my abilities and achievements from it
If you don't want a teacher, then just getting a piano teaching book is a great way to learn and improve
Actually, you don't need to learn notes (sheets) when you have youtube. There are a lot of tutorials where notes are not needed to learn and you just have to remember what to click on :-) EZ these days. But of course, the play with two hands is something which you have to learn by practice and some songs are hard AF even after years
Search for vinheteiro on Youtube, dude has a big following and has a music academy from which you can learn.