Dear Friend Mariko! I am listening to both these videos TODAY. I’m sorry it has taken so long! I will comment on both, but I know they will be very different!
On the first video:
I want to say, very nice bow grip! And congratulations on memorizing!!!!!! The next step is to get the eyes away from the fingers. To train the ears and to get the muscles that memorize the motions required to play, to connect to the ears, you must now play with eyes closed! You don’t have to do that on this piece but playing eyes on bow, and / or eyes closed is the best way to train ears and muscle memory to coordinate.
I also noticed that you are carefully setting and preparing the bow, and this is looking so nice. Try to make the setting completely silent and for this piece, the bow must sound weightless at the beginning of the down bows as you enter the music. One way of doing this is to breathe in, just before the down bow, and exhale as the down bow begins. So it will be as if your breath is blowing the bow downward, like a singer. While you do this, you make the action part of your being. Move your weight from left foot to right foot, to soften the ‘impact’ of the beginning of the down bow stroke.
Also, when you are playing legato, you have to concern yourself with the bow changes at the frog or lower part of the bow. Sometimes, they sound a little tight. Practice 1/4 bows as 8th notes (open string is fine) playing at the bottom of the bow. Let the bow elbow come up in this area of the bow and let the bow elbow move up and down with the bowing. Raising the arm will take some of the weight off the string and soften the sound of the bow changes.
At the end, while playing the open G, vibrato on D3 (which is also G) and the open string will vibrate sympathetically.
I also suggest open string practice on the segments which require slurred notes across string crossings. Get to know what the bow is doing during these string crossings, then add fingers back. Keep the bow elbow rising and falling when you play near the frog.
Where you enter the music with 4th finger, begin the vibrato before the bow starts, breathe in, exhale and begin down bow, move the body with bow direction. You will have then done almost all you could do to make that 4th finger a glorious sound!
Now I will watch the second video:
Oh wow. I think someday you will teach violin!