I cant update my phone keeps on telling me theres an error

What error?

If you're trying to update it wirelessly (via wifi), AND if your device is connected to a reliable Wifi Network with internet access (no personal hptspot, no VPN, no cellular data are allowed), see this support article:--> If your iPhone, iPad or iPod touch won’t update

If the issue persists, try to update it using a computer.

If the issue still persists, contact Apple Support directly, using this link:--> Get Support

Regards

Giulio