……can we……是什么结构？

Only结构做状语置于句首，句子要用部分倒装结构，即将谓语的一部分如助动词、系动词或情态动词放在主语之前。有强调的意思。
"Only after the anaesthetist gave the patient an anaesthetic, could the operation be conducted."
"只有在麻醉师给病人施行麻醉以后,手术才能进行。"

你这句话意思是：只有以这种方式我们才能学习英语。
正常语序为：we can only learn English in this way.
or we can learn English only in this way.

【倒装结构】
倒装共分两类：全部倒装和部分倒装。全部倒装是指将全部谓语动词都放在主语之前。部分倒装是指将谓语的一部分如助动词、系动词或情态动词放在主语之前。如果句中的谓语没有助动词或情态动词，则需添加助动词do, does或did，并将其放在主语之前。


　　A 全部倒装：把全部谓语放在主语前

　　1.there be句型(特殊的全部倒装句型)

　　There are bloody contents, violence and pornography in the Internet.

　　2 .there \ here \ now \ then放在句首时，句子进行全部倒装。

　　Now is the time to take action.

　　3.方位状语开头时，句子进行全部倒装。

　　In books are embalmed the greatest thoughts of all ages.

　　4.主语与表语互换位置(当主语过长而表语过短时，可以把主语与表语互换位置从而构成全部倒装)

　　Well-known is that energy crisis poses a threat to the society.

　　5.伴随状语开头(With或Along with放在句首时，句子应该全部倒装)

　　With globalization have come many problems.

　　B 部分倒装：只将情态动词、助动词或系动词放在主语前

　　1. only +单词、词组、状语从句位于句首，句子进行部分倒装。

　　Only through education can we rise in the world.

　　2.以否定或半否定意义词语（如no, not, never, seldom, little, hardly, at no time, in no way, not until… 等）开头，句子进行部分倒装。

　　Never has this topic failed to fascinate people.

　　3. neither nor开头，句子进行部分倒装。

　　Economic success is not the only factor in achieving happiness, neither is social status.

　　4 .so开头，句子进行部分倒装。

　　Success teaches us something about ourselves. So does failure.

　　5.always \ often \ particularly \ many times \ many a time 放在句首时，句子进行部分倒装。

　　Always am I amazed when I　hear people saying that computers can replace teachers.

　　6.让步状语从句由though或as引导时可用倒装，将表语放在句子最前面。

　　Fascinating as computers utilized in education seem, teachers’roles are more imperative.

　　7 .so that 引导的结果状语从句可用倒装。

　　So severe is this problem that we have no alternative but to take some feasible measures to deal with it.