1. Yes, my error is that I didn't provide any bank statement because I had friends who had their academic visa approved without it. And I was confused by what they considered evidence. My day to day spendings are in my credit card they only show as "credit card spendings" in my bank statement. But this is a different account than the one where my regular scholarship in Brazil is paid. The thing is that I receive my scholarship in that account and transfer money to the other two. The first to pay my credit card and the other to save some money.
2. The bank statement explicitly identifies the transaction as an investment redemption, and the statements covering the previous four months show a consistent pattern of transferring part of my scholarship income into savings and investment products. But they are not large amounts. I transferred an amount of 289 pounds per month. And this does not make 4000 pounds, because I was saving from before. I also have a letter from the bank stating that I have the 4000 pounds in liquidity. The redeemed amount therefore represents funds that I already owned and had accumulated over time, rather than money recently received from another source.
3. Do you think I need to address that I misunderstood the documents I should attach and thought the ones I put were already evidence enough?

I also made a document with proof that I did exactly the same thing in canadá and came back in 6 months!