翻译一句话，挺简单的

When my parents are at home ,they will control the length of time that I'm online.
会错意

when i am at home ,my time online will be controlled by my parents.~

My parents will limite my suferring-time ,when they are at home.

When my parents at home ,they will limit my time on computer.

看起来简单，实际上要理解透彻中文意思再翻译还是没那么简单的。
建议翻译成：My parents do not allow me to surf online for a long time when they are at home. 意思是我父母在家的时候不允许我长时间上网。本质没有变，用法地道并且没有语意歧义和语法错误。
控制在这个地方不能翻译成control，control是掌握的意思。
希望我的回答对你有所帮助。

My parents will control my time of surfing the internet when they are at home.