I can’t back up to my iCloud. I using iTunes doesn’t work too

My iPhone is IPhone 11 Pro Max with 64gb, but because of this problem, the store company where I bought the new phone; they suggested to buy more space and I bought 200gb.

That should be enough.

Tap Cancel Backup if possible.

👉 You need to optimize the range of the mobile network, see this Apple article:

If you see No Service, Searching, or SOS on your iPhone or iPad

If you see No Service, Searching, or SOS on your iPhone or iPad - Apple Support

Then try to free up iPhone device storage see this Apple articles below:

If you need more space for an update on your iPhone, iPad, or iPod touch

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

How to check the storage on your iPhone, iPad and iPod touch

How to check the storage on your iPhone, iPad and iPod touch – Apple Support (UK)

Clear Other storage on your iPhone or iPad

Clear Other storage on your iPhone or iPad - Apple Support

Then try again to do the backup to iCloud.

tried to back up all my info in the cloud to transfer into my new iPhone. They tried several ways but they can’t

Do you have iCloud subscription?

Check -> Go to -> Settings -> your name -> iCloud -> if you see 50 GB (or 200 GB or 2 TB) then you have an iCloud subscription.

iPhone 11 Pro Max

Which iPhone 11 Pro Max do you have? -> with 64GB, 256GB or 512GB?

For example: if you have an iPhone 11 Pro Max with 256 GB, then you need to have 2 TB iCloud subscription.

If you don't have iCloud subscription, see -> Upgrade to iCloud+ -> Upgrade to iCloud+ - Apple Support

See also: iCloud+ plans and pricing -> iCloud+ plans and pricing - Apple Support

Then see -> How to back up your iPhone, iPad, and iPod touch with iCloud

How to back up your iPhone or iPad with iCloud - Apple Support

Do you get any error message?