PC not working after update

I don't think you've been hacked - as Stuart has said restart your computer, making sure you allow Windows all the time it needs to complete the update, and then allow it to reopen and finish loading all the updates. If this is the first update for 3 years there will be a lot of changes and that will take time to allow them all to finish uploading and being installed correctly. (I wouldn't be surprised if that all takes 24 hours as Windows has been seriously upgraded in the last 3 years!) If that process is interrupted that may/will corrupt the install and that may be why you are not being able to access your normal programmes.

I have a Windows 10 machine that I keep for emergencies. Microsoft security updates are all up to date but the last "Feature" update was about 4 years ago. Subsequent Feature updates have attempted to updated but failed. As the "Features" are basically gimmicks I am not bothered as it still works. My main machine is up to date. I do not understand it but not a problem.