"Nie mówiliśmy o tej kwestii."

Translation: We did not speak about this matter.

[Volizione]

Can "sprawa" and "zagadnienie" be used synonymously with "kwestia" when they mean "matter," "question (of)," or "issue?" Are there any nuances in meaning between them?

[vytah]

After checking on sjp.pl:

sprawa is the most common word for "matter", "issue"

zagadnienie is like sprawa, but requiring more consideration and discussion

kwestia is like sprawa, but requiring solving or fixing

But those are minor differences and I am not necessarily sure sjp.pl's definitions adequately reflect the actual usage. I guess you can consider them to be synonyms.

Other more or less synonyms are temat, problem, wątek.

The one other difference is that zagadnienie is practically never joined with another noun in genitive to mean "the issue of X".

[8KAITO8]

• "Sprawa" literally means 'case' or 'matter' (an instance of a problem). Generally it's more or less an everyday thing you have to deal with. For example "Muszę załatwić tę sprawę" = 'I have to deal with this matter'.
• "Kwestia" is similar to "sprawa", however in my opinion it is more formal, like for example "kwestia życia i śmierci" = 'matter of life and death'.
• "Zagadnienie" means more than "kwestia" and is more formal than "sprawa". It means something wider, like 'issue'. For example "Zagadnienie zmian klimatycznych" = 'Issue of a climate change'. You can also say "Sprawa zmian klimatycznych", but this is less formal.

[Walkinthedog]

I believe discuss should work, when we talk talk about something, we are discussind it.

[Jellei]

Makes sense, added.

[Rimdus]

Is it possible to use topic?

[Jellei]

Well, technically it's "temat", but it does seem to work here well. Added.