How to fix your connection is not secure.
The owner of www.google.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.
How to fix
1. set proxy in Firefox browser.
2. open burpsuit and set proxy listenner
3. download certificate cacert.der at http://127.0.0.1:8080
4. add certifacate in firefox , certificate management.
You can download Burpsuite pro 1.7.34
at here : http://destyy.com/w4X1yx
Thank you
hack3r six.