“Has” or “Have” after “Who” in a sentence?

Question

I'm confused about using "has" or "have" after "who". For example:

1. I am a doctor who have confusion in using has or Have.
2. I am a engineer who has 4 year experience, degree in engineering and is available.

Will it vary depending on I or Who?

Answer 1

I am a doctor who has a treadmill.

We are doctors who have an X-ray machine.

I am a professor who has a tweed jacket.

We are professors who have published three papers.

The verb after who should match the object before who. (In the sentence structure you use, the subject [I/We] is independent of the object [professor/professors]):

I know a professor who has grey hair.

We know a professor who has mismatched socks.

I know two plumbers who have leaky sinks.

We saw three mathematicians who have proctectors in their pockets.

To quickly double-check your verb choice, simply remove the subject, predicate, and the who, and make sure it reads correctly:

"We know a doctor who have a new car," becomes "A doctor have a new car." (WRONG)

"We know the nurse who has a new sofa," becomes "The nurse has a new sofa." (RIGHT)

Answer 2

In both your examples, the correct answer is has.

The word has refers to the doctor or engineer, not to I.