ing 是伴随动作,considering it is hard for us to learning English,we should work hard.考虑到学英语很难,我们应该努力学习.
to do 表目的,to 是in order to（为了,表示目的）的缩写形式.TO learn English well,i should work hard.为了学好英语,我应该努力学习.
Do it by yourself.你自己做这件事吧.祈使句.
do not open the door.不要开门.祈使句.
do open the door.do有时放句首表强调语气.