I don't have a partner to practice English with.with有什么用?为什么可以变成practice English with a partner?这是什么知识点?最好 在列举几个例子

What kind of party do you want join in? just like that

同学，这是动词不定式to practice english作前面a partner的定语，
动词不定式做定语，有时与被修饰的名词之间有意义上的动宾关系，（这里面的practice english和a partner就存在动宾关系啊，）如果该不定式动词是不及物动词，它后面需加上适当的介词。如：
There is nothing to worry about.
There are many interesting books to choose from, but I don’t know which to borrow.
老师教你把它变成动宾结构是便于你们判断动词究竟是及物还是不及物。

have a person to talk with
have a pen to write with
你看到了 意思都是一样的 介词宾语结构
当宾语当前面了 介词自然放在最后 不能省略
practice English with a partner 当然可以这样说
这个就是一个正常的顺序

I don't have a partner to practice English with是从practice English with a partner变来的. 由此可以看出with不能省去.
He is sleeping on a bed.
He doesn't have a bed to sleep on.
He's playing with a friend.
He didn't have any friends to play with. (省去with, 必须playing a friend通才行; playing a friend不通)