optimist VS optimistic

I knew or I know optimist is a noun and optimistic is an adjective, but can I use them in the following sentences?

Yes. These are perfectly good sentences:
I am an optimist.
I am an optimistic person.


Please explain and give me 2 examples. I appreciate your assistant or assistance.

An assistant is a

Thank you.
Could you explain why I use a noun in the first sentence and an adjective in the second one please?

The definition of "optimist" is "an optimistic person."

The two expressions are identical in meaning. Either one can be used.

Thank you again.
Shall I use the adjective form when I put person at the end of the sentence ?

What is the difference in meaning between the following two sentences:
The president needs five personal assistants.
The president needs five assistants. "is it rude"?

.

samerrustomShall I use the adjective form when I put person at the end of the sentence ?

Yes.
You can also write "I am optimistic."
But that is your feeling at the moment, not your persona.

samerrustomThe president needs five assistants. "is it rude"?

No, but it is unclear.

"Personal assistant" is a job description. It implies secretarial types of duties.

A Personal Living Assistant is someone who helps an elderly person or a person with with disabilities.