Moto G5 Plus comes with a 4 GB RAM and 32 GB ROM, it also allows to add an external SD card up to 128 GB. When you keep adding photos, videos and audio files and you want to check which of these is occupying more space you can follow the below steps.
Go to File Manager, where it shows the number of Pictures, Audios and Videos. At the bottom of the screen you see Internal Storage and External Storage. Tap on Internal Storage, which will show a graph of what has occupied more. Swipe to the left to see the Storage info on the External card. From the below screenshot, on the External Storage it is Audio which is occupying nearly 5 GB.
With this graphical representation you can easily identify what is occupying more storage and based on this info you can clear to make your phone run smoothly.
There is also a search option where you can search for any particular video / audio / photo when you know the name of the file.