Before starting the method you should have a android mobile which must be rooted.
To know how to root your android device click here
For better view of whatsapp chats you can use your laptop or pc also.
You have to take the mobile of your partner whose whatsaap chats you want to see, for just 2 minutes.
1- Go to File manager of your partners android mobile and then click on whatsapp folder then open the folder named as Database. In Database folder you will find some files which will be named as msgstore.db.crypt.
2- You have to send this file in your mobile via bluetooth, share it or with any medium. Now your 50% work is completed and now you can return your partner's mobile.
3- You have to download an app named as Whatsapp DB Converter from your android play store but remember this app will only run on your mobile if your mobile is rooted. So take care of it.
Note- If this app is not on your play store then,download an apk from the browser.
4- With this app you can convert the file from msgstore.db.crypt to msgstore.db. Now your file named as msgstore.db will be stored in your mobile.
5- In this step you can use your laptop if you want to see good view of the chats and you can use your mobile phone also.Its not mandatory to use laptop or pc. If you are using laptop then you have to first transfer the msgstore.db from your mobile to laptop.
6- Open a website www.recovermessages.com. The view of the site is given in the image below-
8- Click on Accept the terms and then on procesar.Wait for few minutes.
Congratulations,your friend's chat history is infront of you now.