In fact,I think it's clever fou you to think about such a strategy.You can't deny that it's a good way to gain high marks.But maybe because you haven't done that in a righy way ,so you just couldn't get satisfactory marks as you have expected.There is no shortcut leading you to high marks,but continuous training.From your sentences,I can tell your English is good.Maybe what you can do is get a better look at those sentence structures you have learnt,be more familiar with them,and then ,properly make some complex forms.Most important,avoiding misspelled words and grammar mistakes. In fact,I think it's clever fou you to think about such a strategy.You can't deny that it's a good way to gain high marks.But maybe because you haven't done that in a righy way ,so you just couldn't get satisfactory marks as you have expected.There is no shortcut leading you to high marks,but continuous training.From your sentences,I can tell your English is good.Maybe what you can do is get a better look at those sentence structures you have learnt,be more familiar with them,and then ,properly make some complex forms.Most important,avoiding misspelled words and grammar mistakes.