Short Answer: 'Yes', you can.
Sometimes, the changes are beneficial ... 'sometimes', being the operative word.
IF, you are certain, have checked; and, the "Changes" are, NOT correct; and/or, NOT acceptable (for whatever reason); THEN, you can change those changes ...
You can go to the "ChangeLog" for the individual/person (or, Couple) to view the changes; and, change them back again (ie. "Restore"); or, change them to new ones.
Here is the location on an individual's/person's "Person/Details" page/screen to access the "ChangeLog" ...
Here is the URL ...
https://www.familysearch.org/tree/person/changelog/[PID of individual/person]
Let us know if it is a, "Couple"; and/or, a "Parent-Child", Relationship ...
You can can make whatever "Changes" that you may wish by accessing the "Edit" link for whatever "Details" that you wish to change.
I hope this helps.
Before you delete the changes, you might consider messaging the person who has added all this information asking why he thinks this is the same family. Ask for more information, and suggest that the records you currently have on the individual(s) don't corroborate this new information. When I've done this, the person usually responds very positively, and we are able to come to an amicable agreement on the information that is correct for the individuals in question. Hope this helps!
In addition to the answers from @Brett . and @Anne LoForte Willson I would suggest that if you aren't already maintaining your own database, that you create one that is completely under your control. There are several programs that you could choose from ie. Roots Magic, Ancestral Quest, Legacy, and others. Some of the programs are free and others you would be required to purchase. We all make mistakes at times and adding records to an individual that seem to be correct, may be incorrect. Be patient and understanding as you develop your tree, although it is a collaborative one, on FamilySearch Family Tree.