Learn Turkish: Makine tam onun umduğu gibi kusursuz çalıştı. - The machine worked flawlessly, exactly as he hoped.

This uses the formula you are learning: verb + -dık + possessive + gibi. The verb ummak (to hope) gets the -dık suffix, plus the 3rd-person possessive -u, becoming umduğu (the k softens to ğ). Together with gibi (like/as), it translates to "the way he hoped" or "as he hoped".

Is the word onun required here?

Not strictly! Because umduğu already has the 3rd-person possessive suffix (-u), the "he" or "she" is built in. Adding onun just adds a little emphasis, making it "exactly as he hoped", and helps the sentence flow smoothly.

I thought tam meant "full". Why is it translated as "exactly"?

While tam does mean "full" or "complete" when used as an adjective, it is very commonly used as an adverb to mean "exactly" or "precisely". When paired with a gibi phrase, like tam ... gibi, it means "exactly like" or "exactly as".

Why does kusursuz mean "flawlessly" here? Doesn't it mean "flawless"?