I hope you have already designed your own questionnaire in Google Drive with help of Google Forms & Google Spreadsheet. & I assume that you have linked spreadsheet to your google form to collect submitted answers from people.
So to generate mail or notification through mail you have to do following
Navigate to Spreadsheet which is connected to your Google Form your google account.
Click on ‘Tools’ in Toolbar, Click on ‘Notification Rules’
Popup will come up containing header ‘Set Notification Rules’,
Select or check ‘A user submitts a form’ under ‘Notify me at email@example.com when…’
Then under ‘Notify me with…’, Select or check ‘Email – right away’
& It’s done…
Now n you will receive email notification whenever your client submits your questionnaire
Thanks & Regards