Mariko! I’m so proud to see how well you play after only 8 months! That’s really great! I feel like your tone is a little ‘tight’. Do you know what I mean? There is plenty of weight into the string so you’re getting a solid tone. This etude uses all four strings and lots of string crossings so I would work on tone with a much simpler exercise, maybe just open string.
It seems that you are ‘carrying’ the bow instead of letting the bow arm relax a little closer to the body. As a result, most of your bow strokes start at the shoulder. Does your bow arm get tired a lot? It’s probably because it’s always using this big muscle action. So what I suggest is placing the bow on E string. Then let your bow arm drop down next to your body. Find the ‘square’ of your arm by drawing an imaginary line on these four sides: The violin is the top of the square. The bow is the right side of the square. Your lower arm from the elbow to your hand is the bottom of the square. Your upper arm is the left side of the square. When you can visualize the ‘square’, look at your bow where it is sitting on the string. That is where your bow strokes should begin. Now simply open your arm for a down bow, from the elbow. Try to keep the upper arm completely still. Practice this up and down, keeping the upper part of the arm still and the shoulder relaxed. Watch the bow and listen to your sound at the END of each bow stroke. The beginning should have a crisp ‘K’ sound but the end should be open and ringing.
When you play on E string, your bow elbow will be relaxed and close to your body. When you tilt to A, or D, or G, your hand will lead and your elbow will follow. But your bow elbow should always be below the hand, no matter what string you play on.
You may find that you will need to roll your bow hand fingers back on the bow stick a bit. This will allow the bow elbow to drop down and then, when you play from the square of the arm and down bows are opening from the elbow, you will be developing a better sound and a better technique! Good job, Mariko!