I am learning from this website [englishpage.com][1] and I have encountered this:

> No Future in Time Clauses
>
> Like all future forms, the simple future
> cannot be used in clauses beginning with time expressions such as
> when, while, before, after, by the time, as soon as, if, unless, etc.
> Instead of simple future, simple present is used.
> 
> Examples:
> 
> 
>
> - When you will arrive tonight, we will go out for dinner. *Not Correct*
> - When you arrive tonight, we will go out for dinner. *Correct*

Is the above true?

If "yes" then also it is not correct to say for example *"Before you will arrive tonight, we will start the show."* but the correct version will be *"Before you arrive tonight, we will start the show."*

What about this form:  
*When will you arrive tonight?* <= Is it correct?

  [1]: https://www.englishpage.com/verbpage/simplefuture.html