Process Builder, Flow and record level security
Dear experts,
we need to configure the following flow, could you please help us? 
-configuration settings: every user can see only him/her contact records (we set Record Level Security on Contact Object on "Private"),
when a user insert a contact/convert a lead to contact we don't assign a owner (we hid owner assignment)
-when a user1 convert a lead1 to contact1 and select a value on true he will become the owner of the contact.
(The record owner will update on "user1" )
-If an other user2 convert a lead to contact (who is =contact1: has the same Name,Last Name and email of Contact1 record) and select a value on true, the system will send an email to owner1.
 
We tried to create this flow with the process builder and with manage duplicate tool, but it doesn't work correctly, could you please help us?

Trailhead chhalendge:
Create a flow to streamline entry of new accounts, contacts, and opportunities.

error: 
UPSERT --- UPSERT FAILED --- ERRORS : (REQUIRED_FIELD_MISSING) Required fields are missing: [StageName] --- for SFDC record with ID : null,