I was always told at school to never start a sentence with the word "and"...
Evidently I didn't grow up in Russia.
"И' is "and." "A" is a connector from a previous thought, and it can mean either "and" or "but," depending on context
TheFinkie is right. It is bad grammar to start a sentence with "And" - or "А" in Russian as well. However in spoken Russian you can hear it (and many more junk words, like "ну"), but it should NOT be directly translate to English, perhaps as an variation only. The Duo's Russian course lacks of many possible translations in it's database. Duo accepts only limited variations of "entered" translations, sometimes very subjective. It can be frustrating. Just report mistakes and hopefully over the years they will be addressed.
- здесь = in this place (answers the question «где?»),
- сюда = to this place (answers the question «куда?»).
What is wrong with 'and here will we put the couch'? English is not my native language, by the way.
Why isn't "And here's where we will put the couch" an acceptable translation? As a native English speaker, I would never say "And here we will put the couch."
"And here's where we will put the couch" translates as
А здесь, это где мы поставим диван. Or,
А сюда, это куда мы поставим диван. It comes across as laborious and inefficient in the Russian - too many words.
This is a Russian course, not English, so it's not about how common or proper the English translation is, as long as the Russian sentence is understood. Many Russian/English translations do not translate directly.
Also as a native speaker, "And here we will put the couch." sounds perfectly natural. That's not to say your wording is incorrect English; it's fine. I agree that any sentence that shows correct understanding of the Russian could potentially be allowed, but as Vadim points out, there is no "where" in the Russian.