"Eu tenho dado o meu melhor."

Translation: I have been giving my best.

[Deedee222]

Given the construction of the sentence, wouldn't "I have given it my best" by a correct translation?

[Janpot]

"I have given [it] my best" doesnt give away that you are still giving you best.

E g "I have given my best, but noone appreciates you here so now I quit"

The "tenho dado" in Portuguese means that you have been, and are still, giving your best. In that sense the portuguese "present perfect" is different from the English one.

[emeyr]

The pretérito perfeito composto is always translated to the present perfect progressive unless it is used with a stative verb.

You're correct that "I've given [it] my best" describes an completed activity. DL accepted "I have been doing my best" since it implies repeated activities.

[lugosky]

Is this the actual expression used in Portuguese?

[Paulenrique]

Yes! =)

[duofus]

Why not i have done my best ? Very English ! :)

[ThanKwee]

I entered "I have been doing my best" and it was accepted"

[defiantoli]

why is "i have given him my best" incorrect?

[petee0518]

There is no object in the sentence, and your sentence is in the wrong tense.

[dalemorse1]

Why is the article "o" used in this sentence? "...the my best"?

[Paulenrique]

Yes, that's the literal translation. When you have "possessive + noun/adjective", the article is optional.