Clean duplicates in contacts Bitrix24

Bitrix24 cloud. Rate "Company."
The number of contacts in the database exceeded 75к. Sure, 30-50 percent of them doubles.
To clean by regular means is not obtained due to a large number. Even wrote tricky BP, which could twist the contacts have reached the limit of the cloud again, because of the large amount of data.
Now looking for other options. Can somehow upload the entire database in SQL, is there to perform and to understand that with what to combine. And then on the API to make the necessary changes.
When merging contacts, it is important to bear all related entities to preserve the maximum information.

Can we supposed to help? – Then reply and write a specific proposal, estimated budget and implementation period. Answering the questions will be answered without any problems.
If specific ideas – no need to respond.