How to divide 2 document property quick parts in one document by section

That is not possible. When you use one of the "document property" quick parts, you're setting the value in the XML hidden within the document file. All other instances of the same quick part are also attached to the same XML value. Changing any of the instances updates the single XML value, which changes the display in all the other instances of the same quick part.

The solution is to repurpose one or more of the unused quick parts, each of which has its own XML value. You can change the titles of the inserted content controls that display the values, so they all have the same title -- that won't change which XML value goes with each control.

Another alternative is to define custom XML values, and insert content controls attached to them rather than to the built-in XML.

To make this job easier, get the add-in from http://gregmaxey.mvps.org/word_tip_pages/cc_var_bm_doc_prop_tools_addin.html.