I am not doing well in PE.与

I am not doing well in PE.与 do well in 请问;I am not doing well in PE.与The girl doesn't do I'm not doing well in PE.（对划线部分提问） 划线部分是not doing well in PE I am not doing well in maths 中的doing为什么要用动名词形式呢? I am not doing well in ( ).My friend ,Nancy( )better than me I am doing well. I am doing well in school.中的doing是什么意思 I am not doing shit I am not feeling well. i am not feeling well I am doing well in school.中am是什么,是谓语吗? I am doing very well 是什么意思?