http://www.italki.com/groups/2002/topic/43651.htm?src=italki-uhpu-me http://www.italki.com/groups/2002/topic/43746.htm?src=italki-uhpu-me

present perfect’s Sentence structure:have/has + past participle. It means Subject have done sth at present,and it complete already.For example, I have done my home work：Eu fiz o trabalho（by google translate). present perfect continuous' sentence stucure:have been doing (since+ a time point,or for some time). It means Subject has begun doing sth, and is still doing, and will continue until some future time.For example:I have been doing my homework since 10 o'clock.Eu tenho feito minha lição de casa desde 10:00

Present continuous is used when the action is happening...for exemple: Ele está trabalhando agora. He is working now.