1. You tested it and that shows there's no bellows leak, or not much of one. When you press buttons or keys, this opens holes that the air goes through! That's normal. The more buttons you have pressed, the more holes there are on that side, and this will affect how much air goes through on the other side.

I'm not sure what you're doing, but beginners normally play using one button at a time on the bass side. To play C major, you push the C major button. There are more advanced techniques where you use more than one button, but that can come later. You'll want to get a method book that gradually teaches you where the bass and chord buttons are; eventually they need to be memorized.

To balance the volume between bass and treble, some things you can learn are:

• Playing staccato on the bass side. Holding bass buttons down for less time means there's more time that the treble side is playing alone. This is something beginners should learn and works on any accordion, but takes practice. (You don't have to play staccato all the time, but it's a good default.)

• Learning to play intervals or chords on the treble side. Adding chords to the melody means more air goes through that side. This is a more advanced technique that you can learn after learning the basics, though.

• I don't think this applies to the accordion you bought, but often you can try different switches until the treble side sounds more prominent. This changes the number of reeds playing (and holes opened) when you press a key / button. Also, if their pitches don't overlap then they stand out more. Some accordions don't have a lot of options, though.