This article explains how to reclaim storage space on your LG G4 with the Smart Cleaning feature. With the Smart Cleaning you won't need to install any third party app to clean up your smartphone:
Go to Settings > General and then tap on Smart Cleaning. It will scan your phone and display how much space can be reclaimed. First are the Temporary files & raw files which include data from the App Cache, Clip Tray and RAW photos taken with Camera app. The next step is to check the content of Download folder and delete items you don't really need. Finally the Smart Cleaning feature can also detect your Idle apps, which are the apps you haven't use for a certain period of time.