I can’t create iCloud on my iPhone

Your Apple ID say example1@gmail.com is signed in the device .

Maximum limit for creating Apple ID from the hardware address of iphone is three , you can't create more Apple ID accounts , however again sign in with your same Apple ID and it's account credentials ( in fact you have signed out the Apple ID ) in the empty fields or sign in with another apple id that was created from another Mac / iPad or different iPhone .

See the article 

Sign in with your Apple ID - Apple Support

Note : if you are trying to create email account already used from this iPhone say example2@icloud.com this as an Apple ID and maximum limit of creating this mail address has been reused , the account will not be created.

You can use a different Apple ID already created from a different browser and then add the mail account Add an email account to your iPhone, iPad, or iPod touch - Apple Support