How do u wean babies from purees to lumps?

I fed my daughter pureed food from around 5 and a half months, then at 7 months, she stole a piece of toast off my plate and chewed and swallowed it. From then on I just gave her pieces of things to eat. She knew when she was ready to eat. (In hindsight, I should have never bothered with the purees). I suggest you keep going with the purees, but offer your baby pieces of solid food (sweet potato, banana, avocado) on his highchair tray at the same time, or before you spoonfeed.