How we make a car is not a sentence; it's a subordinate clause. It's certainly not a question.
How do we make a car is a sentence, and a question (if it has question intonation, i.e. ?)
Both of them come from the structure
- We make a car
Indef_manner means some indefinite manner or way (of making a car).
Indef_manner is what gets turned into how, the interrogative pronoun for expressions of
manner and means, just as when is the relative/interrogative pronoun for expressions of time.
The difference between the two examples that come from this structure is that
the first sentence has a pronoun in front, but no other change, while
the second sentence has a pronoun in front, and an auxiliary verb before the subject.
Putting the verb before the subject is the mark of a question. So the second one is a question.
The first one is an Embedded Question, or Free Relative, which is a type of complement clause.
Embedded questions do not invert auxiliary verbs with the subject.
- How can they make this car so ugly?
(full sentence; question; auxiliary verb can precedes subject they)
- I don't know how they can make this car so ugly.
(embedded question object complement of know; subject they precedes auxiliary verb can)