Hey Yinmui. My suggestions regarding the 4th finger would be to get your hand higher so that you can reach it. If you force the stretch, this is where other notes can easily get out of tune, and although it seems like the only option, the better one would be to make this adjustment. Any time your fingers are lifting up, you are creating more tension in the hand which actually works against you to reach farther. You would think more effort farther reach, but it is actually the opposite.
Hope that helps!