Original account information vs negative input

Family Search is the best!! I am not an expert but as a researcher, I found that many of my files and input of many years of work were deleted, replaced or tied to the wrong sources that had no ties. How can I preserve all my years of work and still accept other peoples input. I don't mind sharing of information for I am willing to always help, but deleting accurate documented info because the names are alike...difference in years of birth, has become a problem for me in which I find myself correcting all over again 😯. I do have GEDCOM files I can restore from, but three years backup lost😪.

Let's have more options.

Thank you kindly!