Can't speak for your dialect, but in mine, I'd probably be "They've given up / allowed three goals" (or "They've been scored on three times"). Which is quite a different sentence, but may well be what this Swahili sentence actually means: https://en.wiktionary.org/wiki/fungwa. It seems not unlikely that the current suggested translation, "being defeated by three goals," does not accurately convey the meaning of the Swahili sentence. To really be "be defeated by" the verb presumably should have been -shindwa, as used here.
Other discussions for those interested:
Interesting! I have never heard anything like "They've given up / allowed three goals" or "They've been scored on three times", but I speak British not American English.
A BBC sports reporter writes "lose goals" here: https://www.bbc.com/sport/football/45946054
I think you are right - this Swahili sentence about losing/letting in/allowing/giving up three goals has got lost in translation and now gives the wrong impression that it is about losing the whole match/game.
As far as I can see, the match might still be running. If they keep going like this, they might have lost 8 goals by the time the final whistle is blown.
Exactly right. But that's if the word "by" is used. This got added along the way, since the first comment in this thread is objecting to an answer without "by".
Without "by", they have lost 3 goals so far and could lose more; with "by", they lost the whole match with a 3-goal difference, as you suggest.
According to Kamusi ya Kiswahili Sanifu, kufunga has two sports-related meanings: [B] shinda katika mchezo au mashindano (win a game or competition); tia goli (score a goal). It just says the passive voice -fungwa is a possible form in this context but does not give any examples. I guess with that in mind, "they have been defeated by three goals" is a reasonable translation. Would any native speakers care to comment? I think sports jargon is difficult in any language.