Today, Samsung has started rolling-out the Android 5.1.1 Lollipop update for International unlocked variant of Galaxy Note 4 (SM-N910C) Phablet. The US carrier Sprint was already rolling out the same update two weeks ago.
The update comes through Over-The-Air (OTA) and as usual Poland is the first country to get the new update. It brings performance improvements, battery life improvement and security fixes. It should also include a fix for the Stagefright vulnerability unless Samsung is planning to patch that with an additional update.
The OTA update notification should automatically pop up on your device. You can also try to check for the update manually by heading to Settings -> About Device -> Software Update.
If you are a developer then you can try to download and install the official Poland ROM from here.