Hey there! Hope these two storage articles can help!:
https://support.apple.com/en-us/HT203097
https://support.apple.com/en-us/HT211686
If not then they’re maybe a technical reason the storage will not respond, if so, I may try a force restart and try again:
https://support.apple.com/en-us/HT201412
Otherwise, if the storage is accurate, but there’s not enough to support all the content on it, these articles may help:
https://support.apple.com/en-us/HT205703
https://support.apple.com/en-us/HT201656#recommendations
Hope all goes well, otherwise if you needed to, you could backup and restore your phone from a backup, or as new:
Backup:
https://support.apple.com/en-us/HT203977
Restore to factory settings:
https://support.apple.com/en-us/HT201252
Restore from your backup:
https://support.apple.com/en-us/HT204184
on a side note, every once in a while, when having an issue, erasing and restoring the same backup may bring the issue back, unless it is an issue with the operating system, (iOS), that’s usually not a problem. Otherwise, setting it up as new, and restoring the data by signing into your accounts and re downloading your data, and setting up your preferences would need to be done.
I know that’s a lot to take in, hopefully, and most likely the first few steps will fix your issue, hope that’s the case! If need be you can always call Apple Support though, they can also help!