Beginners have all the answers. Experts mostly have better questions.

Early on, everything looks simpler than it is, so the answers come easily and confidently. As you learn more, you meet the exceptions, the cases where the rule breaks, and the confident answers get replaced by more precise questions. You can judge how much someone knows by what they ask.

Next time you want to sound like you know something, try asking the sharpest question you can instead. Write down what you would need to find out in order to be sure. That list is usually more useful than the opinion you were about to give.