I had the same problems initially, but after a while doing this, I'm learning to hear the Gaelic sounds. There seems to be only a loose relationship between what the sound of the written letter is in English and the sound of the written letter in Gàidhlig. Additionally, the lenited sounds have been awfully hard for me to develop an ear for. I play the sentences over and over once I know what they mean until I feel I can hear the differences. shrug I hope that helps.
Was it a type what you hear exercise? Là is listed in the accepted translations but there are a couple of types of exercise where this doesn’t work. We have it in the works to make sure là is accepted for all but it needs to be done as part of a wider batch of changes.