When you enter wrong passcode for multiple times, it should ask for the Gmail account associated with it. So use that Gmail account to reset the code.
If that didn't work, then we can unlock it directly from Samsung Find My Mobile service. This will only work if you have the Find My Mobile option enabled on it. Go to this website --> https://findmymobile.samsung.com/
Login to your Samsung account. Select your device on the left and click Screen Unlock at left column. This will unlock the screen.
If that didn't work, then the only option to get in to the phone is factory-reset it. There is no other way to override the passcode screen if the Gmail option didn't work. Factory reset will erase everything from it and return it to new (like Out of Box). This is how they designed the device. Follow the steps below to factory reset it;
Turn off the phone
Press and hold down Volume Up + Home + Power buttons at the same time for a few seconds.
Android system recovery will be loaded now
Select wipe data/factory reset. (Volume buttons to go up or down, select with Power button)
Select Yes — delete all user data.
Then select reboot system now
That should factory reset the phone . Please let me know if that didn't work, so we can continue troubleshooting.