Samsung Galaxy S6 — Problems After the Marshmallow Update

After the Marshmallow update, many (I have no way of knowing the exact number) of my contacts were combined.
A person will come through with the correct picture and phone number, but someone else's name. My son came thru with his picture, his phone number, but had my friend's name. Her name and phone numbers are all in his account!!
Another of my girl friends came through with the name of "Warranty Center"!!
If I'm not familiar with every person's cell number, I can't tell which is the correct number! Talk about a big mess!!