We don't know the weather tomorrow
=It (is )(unknown )the weather tomorrow.If youkeep doing () this for along time,you are sure have great ( ) in your study.If youkeep doing ( on ) this for along time,you are sure to(貌似少了to) have great ( progress/improvement) in your study.还有前面那个is unknown感觉不大对 还是用depends on比较好 采纳哦