be sure that+从句和do better什么意思

be sure that+从句
确定某事
do better
做更好

be sure that
是能够肯定的意思
例：He is sure that the apple is red.
do better
应该是做得更好的意思，主要得看语境
例：he do better than her.他比她做得更好。
或者更深一点，do还可以做强调的意思，就是
他的确比她更好。