"it takes a few seconds" should be acceptable
I disagree. There's a slightly different meaning to taking a few seconds or taking several seconds in both English and Swedish. Taking a few seconds would be några sekunder in Swedish.
I agree. This would be the common English use. "It takes a few seconds", then "it takes some seconds" then maybe "it takes several seconds" - but they all mean the same thing.
I agree that "it takes several seconds" sounds unnatural but i suppose the purpose is to have more of an accurate translation and to better understand Swedish.
How I know when flera means many and when few/several?
It never means many. Many is - många