Hi! This sometimes happens to me on my own phone. The two solutions are to either migrate some of the data (photos, music, downloads, etc.) from your internal storage to your SD card, or move apps from your internal storage to SD card.
I'd recommend getting a file manager from the play store to see what is taking up so much space on your internal storage. [https://play.google.com/store/apps/details?id=com.rhmsoft.fm|This file manager] should do the trick. Once you have that installed you can look in your ''Downloads'', ''Music'', and ''DCIM'' (pictures) folders and see if there are any large files that you can delete. If there is a large group of music, pictures, etc. that you don't want to delete, but don't want on your internal storage, you can use the file manager to move them. This can be done by long pressing the folder/file name, selecting "move" from the options, and then navigating to the SD card and selecting "paste".
Here's a list of YouTube videos that explain how to do this. [https://www.youtube.com/results?search_query=how+to+move+files+from+internal+memory+to+sd+card+.|Videos].
This video in particular should be helpful for moving both files and apps to your SD card. [https://www.youtube.com/watch?v=wsFZJS8kV4E|Video]
Hope it works out!