I’m not being able to update my ios

Follow all the steps provided in this upport article:--> If your iPhone, iPad or iPod touch won’t update

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

Regards

Giulio

Hard to say if you don't tell us what happens when you try...

What iOS version is currently running on your 11?

How are you trying to update it, wirelessly (via wifi) or using a computer?

What error message are you getting when you try?