If you just want to learn a song, you can usually do it in a couple hours.
If you want to play music for yourself, usually around 3-6 months.
If you want to play in a group, or for an audience, you are looking at 6-12 months.
If you want to compose your own music, 6-9 months.
If you want to understand every tiny aspect of music theory, every symbol, be able to read any piece of sheet music as fast as you first read it, and be able to teach university classes on it… decades.
So, the first thing you need to do is decide on what skill level you are trying to achieve. It will change the approach you take, and the method you use

All sound is caused by vibration. When we think of sound, we usually think of vibrations in the air. You can hear through anything—it’s the vibrations. For example, you can hear underwater or with your ear pressed against a door. It’s still sound, just not through the air. The speed at which the vibration goes back and forth is called the “frequency.”

Different frequencies sound higher or lower. The faster the frequency, the higher the note. The lower the frequency, the lower the tone.

Take the average man’s voice. His vocal cords vibrate around 85-155 times per second to produce his voice. The average woman’s voice is closer to 165-255 vibrations per second. We all have a specific range that varies from person to person. And usually, you can increase your range with practice, but there is a physical limitation to the vocal cords.

Some specific frequencies are called notes. They are individual units of sound. On a keyboard, each key plays a different note. Being slightly off the specific frequency is called “off-key.” Setting an instrument to the correct frequency is called “tuning.”

Over the centuries, there have been some shifts in what the “correct” frequency was for different notes. Even today, there is some variation in what the correct frequency should be. But nowadays, they are all relatively closely tuned.

A piano makes sound when you press a key by having a little hammer inside hit a wire. Generally, the shorter wires vibrate faster, while the longer ones vibrate slower. Thicker wires vibrate more slowly and thinner ones vibrate faster, as well.

The further left the key is on the piano, the longer or thicker the wire inside, the slower the vibration, and the lower the note. The further to the right, the shorter or thinner the wire inside, the faster the vibration, and the higher the note.

There is a pattern in frequencies. Once the frequency doubles, it plays the same note again at a higher pitch. Each set of frequencies is called an octave.

So, we get recurring notes up and down in higher or lower octaves.

In music, we use 12 different notes in each octave. They are evenly spaced out and fit into the frequencies very evenly.
Each key on a piano keyboard represents one of the 12 notes in an octave. There isn’t anything special about them being white or black. Not if we are looking at what makes music.