Hi Markus_F
I may be misunderstanding from your description - but if that .json you supplied is a response and you just need to grab 2 node values from the .json response - you can use a property transfer with a properties step to allow you to use the values later on in your test.
i.e. so your step hierarchy in the test would be something like the following:
POST --> generates the .json response you mention
Property Transfer (grabs the 2 attribute values you want to use later and populates the Properties step with these)
Properties step (the values transferred to this step from the original POST via the Property Transfer step)
The way to do what you want is as follows:
Run your POST to generate the response.
Highlight the first attribute you want to transfer
Click on the 'Transfer To' dropdown to launch the menu
Select 'Add Properties step' (this will generate the property transfer step AND the Properties step)
Click ok to select the name of the target property
'Transfer to Property' form launches, click on ok to accept the defaults
For the second attribute you want to grab
Highlight the second attribute you want to transfer in the .json response
Click on the 'Transfer To' button to launch the menu
Select the relevant step that is the Properties test step created when the first attribute transfer was created
Select 'new' to create a new property to hold the json attribute value
Click ok to select the name of the target property
Transfer to Property form launches, click on ok to accept the defaults
At this point click on the Property Transfer step, click on each of the transfer and make sure both the Source and Target attributes are correctly populated - I've just run through this and I noticed that the second transfer's Target 'Property' field in the property transfer step is blank (might be a ReadyAPI! defect - as I keep doing this and it's always blank by default) - so I just set it to correct Property name (that is defined in the Properties step).
If you now run your test (ensuring the Property Transfer step is BEFORE the Properties step) - the values you want to save for subsequent usage will be saved within your Properties step.
Hope this helps!
rich