The word "mukava" also means "nice", am I right?
Yes, which is confusing to me. Lol. A sofa can be nice and not be comfortable.
I agree with Beerzoe. I would also use the shortened version of comfortable 'comfy' though that might be too colloquial?
Would a 'nice sofa' be accepted here?
In Finnish "mukava" in the sense of "nice" is only used to mean friendly people. A nice sofa would be "kiva sohva". "Mukava sohva" only means a comfortable piece of furniture which doesn't necessarily look nice at all.