Q: I try to restore my iPhone through iTunes, but I tried 5-6 times already. What should I do?

Try Recovery Mode:

Connect your device to your computer and open iTunes.

While your device is connected, force restart it: Press and hold both the Sleep/Wake and Home button for at least 10 seconds, and don't release when you see the Apple logo.

Keep holding until you see the recovery mode screen and wait for it to restore.

You may have to do the above more than once as recovery mode is difficult to get into.

Restore as New first and test it. Then restore from backup if desired. If the backup is corrupted it will likely bring back the issue.

https://support.apple.com/en-us/HT201263

If the above steps do not help, you may have to take it to an Apple store for testing.

Get help with iOS update and restore errors - Apple Support

Temporarily  disable or remove any anti-virus and firewall software you have installed.

Check for communication issues

If you see error 1671, iTunes is downloading necessary software. Wait for the download to finish and try again. To see how long the download should take, you can click the down arrow in the upper-right corner of iTunes.

If you see one of the issues below, your computer might not be able to connect to Apple servers or your iPhone, iPad, or iPod touch:

• 17, 1638, 3014, 3194, 3000, 3002, 3004, 3013, 3014, 3015, 3194, 3200
• "There was a problem downloading the software."
• "The device isn't eligible for the requested build."

Check for communication issues between iTunes and Apple software-update servers. Also check for issues with third-party security software.

If you still see an error message, contact Apple Support.

Just to be sure what version of iTunes do you have? The latest is 12.4.3. If you don't have it, update to it.

Also are you on a Mac or a PC? If a PC try deleting and reinstalling iTunes, it resolve many issues.

Remove and reinstall iTunes and related software components for Windows Vista, Windows 7, or Windows 8 - Apple Support