As is known to us all, we can use iTunes to back up our iPhone data. When we lose important data such as contacts, photos, videos, etc., we can reset our iPhone and then restore these data from iTunes by setting the iPhone up again. However, this may cause another problem - all the existing data on iPhone will be replaced by the previous backup we synced, which means we will lose the data created after the synced backup we choose. Then, is it possible for us to keep that part of data? Actually, it is possible as long as we extract WhatsApp messages from iPhone backup.

Then, how to extract the data we want? Look at this post and have a try:
Extract WhatsApp Messages from iPhone Backup


Hope it will be helpful for you!