Open the Settings on your Android device and look for Apps & Notifications. Select that, then scroll and find Languinis.
After selecting the game from the list, you will be brought to a screen that has the options to turn off notifications.
Open the Settings on your iOS device and scroll all the way down the left hand menu to find Languinis in the list of apps.
When you tap the game, a menu should open in the right that has "Allow Languinis To Access > Notifications" Select that and you can view all of the Notifications settings for the game, along with the option to disable them.