hi jilian! i think it depends on you! if you have already learnt some part of that language, i am sure you have achieved a certain level, so you can start from that level. EX. if you have enough confidence for reading, you can start from listening. why to start from ABCD when you have already spent some time on that language. time is so expensive!

Hello Jilian, You will have not completely forgotten, what you learned previously . A quick revision is essential to recollect all you learned before. The longer the period of time that passed between your initial learning and your relearning process , the more effort and time you will need to recollect what has been partly forgotten or to refresh your memory. While revising you will sense, that it is easier and quicker to relearn than learning something for the first time, whether vocabulary or grammar rule.