Share 2 list rcords into 1 list based on userid to showtotal using c#

Question

Greetings

Using sharepoint 2016 on Prem

having 2 list like below

 

 

i want to validate record between 2 lists which is List A and List B.

if same record exist on list B based on "User ID" so it should merge the record into 1 record to sum up.

Note: if User "A" not exist on List B so it should transfer data into List C
But if User "A" record exist in list "B" so it should merge the record into 1 with sum up on count (Total Docs uploaded).

my output would be like this it should be in desc order based on "Total Docs uploaded'

 

Note:Want to do it programmatically

Thanks