i make good efforts to learn english so as to be a volunteer 这句英文有什么问题吗？？？

Firstly, without considering the meaning of this sentence, it should be phrazed as "i make good efforts in learning english so as to become a volunteer".

Secondly, if you consider about the meaning of the sentence, there presents a logic error. Does becoming a volunteer necessarily require any english skills? It could be rather ambiguous if u phraze in that way.

I making every effort to improve my english so that I can be a volunteer.
我会这样说，但不知道你哪里不对

"so as to be" is the problem
but really i think your whole sentence is rather ambiguous

it will be better if you rephrase your sentence to:

I spent great effort to learn english, so I believe I am good enought to be a volunteer.