Jottings from Ciberdvidas, with some side-notes pulled from other places:
General Meanings of Ainda
Most simply, it’s just “still” e.g. “Ainda estás a adormecer?”
It can mean “one day” as in the example “Tu ainda hás-de ser muito feliz” (“you’ll be happy one day”)
It can be a reinforcer – like mesmo – but applied to a specific time as in the example “Ainda ontem o vi” (“I saw him only yesterday”)
It can work like “além disso” as in the example “Fui jantar. Comi muito bem e ainda me diverti com a conversa de Miguel” (but cf the note to this text where I used the phrase “ainda por cima” which has more of a sense that the thing being added to the situation is making ot even worse, rather than even better!)
It can mean “at least “Ainda se ele marcasse um golo, o dinheiro era bem gasto, mas assim…”
Interesting that you can imagine english sentences that would meet all these cases and would all use “still”, because it’s one of those words that can be used in places where it doesn’t have a real meaning but subtly tweaks the existing meaning of the sentence.
General Meanings of Já
Under normal circs, it means “already”, but like the use of that word in jewish slang, it can also mean “right now”. “Vou-me já embora” means “I’m going right now”
Já in questions/answers
If a question contains the word “já” and you want toanswer affirmatively you’d normally use “já”. Otherwise,”Ainda nao”
“Já comeste?” / “Já sim”
“Já leste o artigo?” / “Ainda não”
Ainda in questions/answers
Likewise, if the question contains ainda then the answer would normally contain ainda in the positive and já in the negative
“Ainda estudas português?” / “Sim, ainda estudo”
“Ainda estuda japonês?”/ “já não”
With “que”
“Ainda que” is “Although” and it’s followed by a subjunctive
“Ainda que eu esteja de regime, às vezes como gelado”
Já que is “since ” and doesn’t
“Não tenho tempo para estudar já que comecei o meu novo projecto”
Other Locutions
Ainda bem = “It’s just as well”
Ainda assim = “Even so”
Ainda mais = “Even more”
Desde já = “As of this moment”
Luso 