I have problems playing the G# - E - C# - G# passage in the left hand. Because of that E it gets really sloppy, cause I have difficulties pressing the key from higher place while still maintaining even volume. Any tips for practice?
Try practising it as a chord (playing all four notes at the same time) to help get used to the hand position and depth of the E key. Then when that sounds and feels even and balanced try it again as written.
The other answers are very good, but I would like to elaborate on Xcoder's, and add something about hand position.
I think you want the position of your second finger to be very arched. Rather then "playing flat", with your second finger mostly horizontal you want a lot of bend at the first knuckle. That will make your finger more like a little hammer, and make it more precise when it strikes the key.
To improve your practicing on these kinds of passages, I would recommend "rythmetizing" things like this. Turn the metronome down, and change the rhythm. Here you could do repetitions of "short-long", "long short", and also triplets "ta tri-pa-le" as well as "tri-pa-le ta". Do that cleanly, with the exactly artitulation you want to have when you play it. Then crank up the metronome and repeat. It will make the entire thing easier to get smooth.
A good way to practice these kinds of passages is to use a metronome. Start out slow, depending on the tempo of the piece. Make sure you lift your fingers and articulate every note. Start out by playing every note loud in order to get a feel of the notes under your fingers, and then follow the dynamics as you get used to it. Gradually increase the tempo of the metronome.
In my experience there are two frequent mistakes in cases like this.
- The hands position is too much at the outer part of the keys. The keys are very long and we can touch them everywhere. In this example, the third finger usually is at the very beginning of the c# key.
- The fingers, especially the third in this case, are holded above the keys while playing the piece, instead of resting on them. Therefor the distance between the fingers and the keys is different for all keys and so the time needed to play a note is different.
You can try to transpose this bar to other keys, which can help for the second point.