“好好学习，天天向上”的英文是：Study well(hard)and make progress every day.

You can still be ready for the exams if you will lay yourself down to your study during the remaining three weeks.
我多么后悔在树林和田野浪费的时间，那是我本该好好学习和贪玩荒废了的日子。

How I regretted the hours loafed away in the woods and fields,the days when I had played and should have studied.
从这儿以后，我们要好好学习。

From now on we'll study hard.
你把它好好修一修可以吗？

Could you give it good trimming?
在外语学习上没有捷径，我们必须每天练习，只有这样我们才能精通它。

There is no short cut in the study of a foreign language.We must have drills every day.Only in this way can we have a good command of it.
我天天学习英语。