You need to be careful while downgrading to the previous version of Windows. Follow the steps below -
1. Back up everything that you would not want to lose. Software upgrades and downgrades can cause data loss.
2. If you have signed in to any accounts or created any new accounts, sign out from all of them and remove them from main account.
3. Click on Start and then .
4. Click on Update & Security.
5. In the next screen click on Recovery.
6. On the next screen locate Go Back To Windows X where X stands for your previous version of Windows.
7. Click on Get Started. On the ensuing screen, you will be asked the reason for downgrading. Select the appropriate one and click Next.
8. Windows provides you a list of precautions. Note them down if you want.
9. Click on Next. Windows will now begin downgrading your system.
Please note that some of your apps may stop working. Reinstall them if needed.
Since you want to come back to Windows 10 after downgrading, you will need to get your Windows 7 working properly. After that, you are free to upgrade to Windows 10 again.
Live....and Let Live!