The AttributeValueMapper should be filled with specific values to map, like this: 
 

You're probably looking for a FeatureJoiner or FeatureMerger to perform a join between the WFS data and your Excel sheet (although it would help if you could show a small example of both)

Thank you for your replay.  There is no common ID with my excel file which enables me to use Feature joint.  I thought I would use the excel file  by importing in the menu of Attribute mapping   instead of manually mapping the correct the names.

You can do that by using the Import button (lower right)

 Beste @redgeographics 

  I already saw the import button, but I am not succding to make mapping.  I couldn’t indicate the Exact columns and rows(like H2:

 Beste @redgeographics 

  I already saw the import button, but I am not succding to make mapping.  I couldn’t indicate the Exact columns and rows(like H2:

 

Basically both columns need to be filled with values. So in your case eigenaar names. See my previous screenshot, where the first row should be read as “if eigenaar is Jan then eigenaar_new becomes Hans”

You can enter the values manually or read them from an existing dataset or feature cache by using the Import button. In that case you can pick whether you want to import them as Input or Output values.

Chances are that if you have an Excel with both input and output values you don’t need to use the AttributeValueMapper (it has the disadavantage that it can only be edited in FME itself and it is not dynamic) but can join it to your data. 

If you can show me what your data looks like and what your Excel looks like I can try to help you.

 You are right,  I will find a way to join the excel list and wfs