Being a Technical Professional for more than three (3) decades now, I could spot pretenders very easily. If I say pretenders, I am not referring to the English-American rock band in the late 70's. I am referring to those people who never say "I do not know" hoping that nobody will ever find out the truth about them. This attitude is dangerous in any situation.
It is a common misconception that saying "I do not know makes someone a lesser person". It is not. It will actually shows how humble someone to admit not to know. Likewise, someone will learn more by asking. No one knows everything. On the contrary, if you know more than others, do not be bragging about it. Someone out there knows more than you do.
"If you’re the smartest person in the room, you’re in the wrong room." - Marissa Meyer
Don’t stay the smartest person in your room for long. Remove the ego. Walk out of that room and start over. It's not about how smart you are. It's about how steep your learning curve is.
If you don't know, Ask...
Saying "I don't know" will not make you a lesser person. In project implementation, this attitude will save the project from jeopardy. If you don't know, ask. Rather that pretending to complete something you could not deliver competently later on, it would be much better to ask for help early so that other people could extend help on you before the issue escalates to an uncontrollable monster.
The problem is you don’t know what you don’t know.
"You don't know what you don't know" always to remind us that there were things about the situation which we didn't know.
We all able to learn only by asking questions. It's not stupidity.