I'm worried because my English isn't-----（improve）为什么? 翻译下面的

I'm worried because my English isn't_____（improve）为什么? 翻译下面的： the virus stays in you loI'm worried because my English isn't_____（improve）为什么? 翻译下面的： 1.the virus stays in you longer because your body doesn`t have a way to kill it.2.bodies can do a great job by themselves答案填写的是improving,我也不知道为什么？