First let me thank you for teaching me a new English word: I had no idea "toldo" was "awning"! :-)
It started to rain, let's go under(?) the awning of the café. CORRECT
If it´s "under", can I use "debaixo de" here: "vamos debaixo do toldo"? No.*
But rethinking about this, the most accurate sentence would be:
Começou a chover, vamos para debaixo do toldo do café. "vamos para" + "debaixo de".
I'm sorry for not being clear on this. Still, the sentence as I wrote it yesterday would work perfectly in the given situation, I believe I would say it like that and no-one (native speakers) would even notice.
"debaixo de" is a static expression, doesn't go well with movement. (Re read the second example I wrote yesterday.)
1 - Let's go down to the basement.
Vamos para baixo, na cave. NO. Could be: Vamos lá para baixo, para a cave.
2 - Look there, below that window.
Olha lá, abaixo da aquela janela. No. Could be: Olha ali, por baixo (another one!) daquela janela.
3 - He's living below, on the second floor.
Ele está a morar abaixo, no segundo andar. No. Could be: Ele mora/está a morar por baixo, no segundo andar. or Ele mora lá em baixo, no segundo andar.
4 - The pen is under the bed.
A caneta está debaixo da cama. CORRECT
5 - Where is he? He's already down in the lobby.
Onde ele está? Ele já está em baixo, no vestíbulo. Almost. Could be: Onde é que ele está? Ele já está lá em baixo, na entrada (more common than "vestíbulo").
After reading all this, you'll probably ask me "Why do you need "lá" in sentences 1, 3b and 5?" The truth is I don't know why, I just know that that's how we say them. Sorry!
For some time I've been asking to change some words in different courses in "discussions" for those words. Mainly it's the articles. Some have definite articles, some have indefinite articles, some have none - so I asked to add the missing ones to alternatives, so that I wouldn't get wrong answers.
Usually (well, always) it's always Ben who answers with "Added, thanks", so I thought maybe I should save the trouble for both of us becoming a curator and doing it myself.
I intend to change (mostly add to alternatives) only things I'm already familiar with. For those that I'm nor sure about, I leave a question in "discussions" (though nobody ever answers - you seem to be the only portuguese-speaking person here).
About the discussions, when you leave a question, either in a forum or in a word, could you also leave the link to it in my garden wall? That way I would be notified and could address the issue sooner than later (i.e. without having to accidentally bump into the question). Well, not really when you post in the Portuguese forum (because I come here on a regular basis), but when you ask something in the discussion space of a given word.