Family Historian User Group

My laptop recently crashed, corrupting the disc, and I have lost nearly a year's worth of work. (my last backup was January 2021). I have over 40,000 individuals in my FH 6 project but only 5,000 are direct ancestors. Fortunately, I uploaded that smaller file onto the Ancestry website about 5 months ago so anticipate there may be a few individuals on there that are missing from my older desktop version. I am very wary about Merged as I've seen the mess and duplication than can ensue. I presume I firstly just download the Ancestry Gedcom into my laptop but then how do I ensure that the programme selects from it only those entries missing from my main project file and attached them in the right places?
Thanks

Have you read all the advice in
Merge/Compare File

What are your plans to prevent such a catastrophe from happening again?
There are regular postings here and in the Email forum about backup strategies and users who have suffered crashes.
I am always gobsmacked that anyone does not have a backup regime.
See FHUG Knowledge Base Backup and Recovery advice where from Making a Safe Backup onwards there is guidance on strategies which ideally should be automated.