Doing a reset that keeps anything on the device will not help, a "Hard Reset" would be needed. But that won't correct everything. I am going to include the best steps below.
1. First, do a "Hard Reset" (instructions below) of the device. Do not change any passwords prior to this.
2. Once the "Hard Reset" is done, start the set up of the tablet again, adding your Google account info, but do not add any apps or files at this time.
3. Once you have your account added to the tablet, log out of the account on the tablet. Yes I know that seems odd, but there is a reason.
4. Now log into your Google account from a different device and NOT from the tablet (preferably a computer).
5. From this other device, change your Google password.
6. Now log into your account on the tablet using the new password.
7. At this point you are going to need to change any and all passwords for any apps, sites, etc., that you ever logged into from that tablet before. They are all at risk still. This includes all of them, anything you logged into from the tablet. Once those have all been changed your should be clear.
8. Now when you reinstall any apps or files, be sure you are careful. Apps can lead to problems too. So be wise on what ones you install.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the "Volume Up" buttons, together, until you see the start-up logo on the screen.
4. Once you can see the logo, release the buttons and allow the device to enter the "System Recovery Mode".
5. Next use "Volume Down" button to get to the "wipe data/factory reset" option.
6. When in recovery mode the "Volume Up" and "Volume Down" buttons are how to can navigate and highlight what option you need.
7. Once you have selected the "wipe data/factory reset", press the "Power" button to select that option.
8. On the following screen, repeatedly press the "Volume Down" button until the "Yes - delete all user data" option is what is selected.
9. Then press the "Power" button to hard reset the tablet.
10. If you took your SD card out in step 2, when the device is up and running again, reinsert the SD card.