In your code you have a [`Symbol`](http://reference.wolfram.com/mathematica/ref/Symbol.html) `s` that is not declared before the line `Begin` line. Because of this it is created in that specified ``Afak10`Private` `` context. (Also, your code presently has an error; it needs to be ``Begin["Private`"]``.) You can include the ``Global` `` context if that is in fact the Symbol you wish to return:

 f[x_] := Module[{}, x^2 + Global`s]; (* as part of your package *)

Now using the function:

 f[z]

> s + z^2

Nevertheless I caution you about this method as you generally should not use (plain) global Symbols like this; instead use [Formal Symbols][1] which are [`Protected`](http://reference.wolfram.com/mathematica/ref/Protected.html) to prevent accidental assignment.

 f[x_] := Module[{}, x^2 + \[FormalS]];

It looks like this:

![enter image description here][2]


 [1]: http://reference.wolfram.com/mathematica/ref/character/FormalS.html
 [2]: https://i.sstatic.net/GfPvZ.png