It is quiet difficult , specially with the vowels ( u) , (e) ,and specially if your mother tongue doesnt have similar pronounciations but you have to listen to words and repeat them , until you get the sound .you can do with a teacher who says them and you repeat or by using audio material like cds or online lessons .:)

oi, nao endendo bem sua pergunta i haven't really understood your question j'ai pas bien compris le sens de ta question