Here I am going to show you how to free some spaces on your iPhone running iOS 11.4 There are a lot of ways to save your storage while it is being full. The tip I am showing you is one of them and this one is very effective.
1. Go to Setting
2. General
3. iPhone Storage
4. Offload Unused Apps
Her is an interesting point. Offload Unused Apps will uninstall the app that you didn't use them for a very long time and you are on low storage state.
5. You can Offload for all the unused apps or one by one. To do so, there is a list of all the apps and you can select one or more to offload. The offloaded apps will automatically uninstall(the icons of the app will still available on the home screen) the data of the app but you will be able to use it later.
6. When you would like to use those apps again, just click on those icons and it will start download the apps for you use again.
Advantage: Help you to have more space when you are on low storage mode.
Disadvantage: Requires data connection when you want to use the apps again.
Here is the link to the video showing you more detail.