I'm playing the piano since 2 years now. Currently, I started playing this piece. It mainly consists of chords and since it's written in Bb Minor, there are many black keys. How do I practice these chords? My hands are pretty small (I can play an octave). Any tipps would be appreciated!
How old are you (I'm only asking to find out whether your hands will grow, no need for a specific age)?
There are some things you could do. For a start, I'd do what I have been doing for years: practise all your scales with their diatonic chords every day. No need to practise in all 12 keys. You can dedicate 6 days of the week to 2 keys each and revise them all on the 7th day.
Are you following a good system with regard to your practising in general? I highly recommend "Fundamentals of Piano Practice" by Chuan C. Chang.
If your hands are not growing any time soon, there are some workarounds for more difficult cases as well. Remember that the most important notes in every chord are the 3rd and the 7th. If you cannot play all the required notes, you can just play those 2.
You could invest some time into finger-stretching and wrist exercises as well. Make sure your fingers end up on top of the keys and take things very slowly. Play the same chord over and over, making sure your posture is proper, and that your fingers are relaxed and correctly positioned on top of the keys. Often extended practising and anxiety can make our joints too stressed to properly work with an instrument (I play instruments with keys too, and I always invest some time before any practice session to ensure I am breathing properly and none of my joints are strained or feel "unnatural" in some way).
These chords are all less than an octave. So you should be able to reach the notes. You’ll notice the hands are placed on the black keys and the white keys are played in between You need to do this. This requires more strength than stretch as you need to play further up the fulcrum of the white key. I would highly recommend a good teacher if you wish to play at this level of technique.