Hi my name is ***** ***** I will be the expert working with you today to help and resolve the problem you have posted.
I am sorry to hear that you are having such trouble. I will try my best to help you out and resolve the problem as quick as possible.
Its is a long process you would need follow many steps
Back up your Mac Create a bootable drive of OS X El Capitan Erase macOS Sierra Reinstall OS X El Capitan Restore data from an earlier El Capitan Time machine backup
If you are ready let me know i will provide you step by step instructions however it will take a whole day process.
Sierra is a brand new update and if you keep working on it the speed will gradually increase and it will be back as it was before.
Bugs need to be removed and fixed as Apple is working 24/7 on it.
What is not allowing you to enter the mobile number.
I will open the question to other experts for there views.
Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
Are you sure you want to downgrade to El Capitan or previous version ?
It is not a straight forward process. For that, you have to get an external hard drive, backup all your files manually, then get an 8GB flash drive and make a bootable El capitan drive and boot into it. Then erase the hard drive, reinstall El Capitan and then restore files from external hard drive.
So start we need;
An external hard drive to backup your files
8GB or higher capacity flash/thumb drive.
Do you have these devices ?
Hi there, Sorry for the delay. Yes, it is better to used to Sierra. Sooner or later, you will have to upgrade any way.
Not sure about the iTunes. Apple changed the design though and they will keep changing it. Sierra is still new and has lots of bugs, but Apple will release fixes soon. If you need any help with anything in Sierra, please let me know.
Have a great day,