I cannot open my iPhone as I need the original iCloud password

See this article:--> If you forgot your Apple ID password - Apple Support

Did you buy that device as second hand device? Should be this case, only the previous owner can unlock that device, using (or letting you know) the credentials that were used to activate that model 5. Without those credentials, that iPhone is useless to you.

Regards

Giulio

Okay.

If you're talking about your Apple ID password, see my previous reply (first line).

If you're talking about the passcode to unlock your screen, follow these instructions:--> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled

Regards

Giulio

Start here: https://support.apple.com/en-us/HT201487