NOTE [1]

To: All staff
From: Spencer , HR Management

Dear Staff,

I'm glad [2] to inform you that I feel honored to have invited Ming Yang [3], a famous [4] doctor who has worked as a specialist for more than ten years, to give a lecture on healthcare. It is a good opportuntiy for us to learn gain [5] some knowledge about daily healthcare.

Please join the lecture at 4 p.m. this Friday in the conference room.

Thanks for your attention.

Kind Regards,
Spencer

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[1] A better word here would be 'Notice'.  (I know the task describing writing a 'note'.)  A note is something you write for yourself or for one other person.  A notice is a document which is sent to many people.

[2] A better word would be 'pleased'.  'Glad' is an uncommon word.  In fact, I cannot think of any occasion when we would say 'glad' rather than 'happy' or 'pleased'.

[3] A doctor would usually have the title 'Dr.': "I have invited Dr. Ming Yang to visit us."

[4 Someone can be famous for dubious reasons.  It would be more polite to say that he or she is a well-regarded doctor, or a highly-respected doctor, or a renowned doctor.

[5] 'Knowledge' is something a person has.  You can gain or increase knowledge by studying and learning, but you cannot study or learn knowledge itself.

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Great job!  There was only one real correction.  The remaining comments were merely suggestions.