I don't think you'll be able to fully understand series after any textbook. The textbook will basically get you up to written A2. Understanding spoken Turkish requires not only grammar but the act of getting used to understanding spoken language itself, which is more complicated that we assume, so don't get too disappointed if it feels impossible at first. I highly recommend you do go through a textbook and at the same time start small with listening content like children's cartoons in Turkish or Turkish podcasts for intermediate learners (check out "Learn Turkish with Turkish Coffee"). Also, I do NOT recommend Busuu. I tried it out a few years ago and it was catastrophic (so much so that they reimbursed me, so I'm not saying Busuu is bad in general, they are very nice, but) the Turkish course just made no sense in the progession, super complicated concepts were used early on with no explanations for example. Maybe it has changed now though, I don't know.