My iphone 11 pro connecting Wifi and mobile network become very slow

Continued from my above reply.

sccatke Said:

"My iphone 11 pro connecting Wifi and mobile network become very slow[...]Additionly,I can't connect to Appstore anymore and Apple server always failed to me after tying Apple ID password. Please fix this problem if possible."

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Troubleshooting a Locked Account:

Locked Out:

For note: You are you locked out of your Apple Account. There is no iCloud account.

So, Contact Apple Support:

Visit this Link: If your Apple ID is Locked or Disabled - Apple Support

Why Accounts Become Locked:

When your iTunes Account has been disabled, and that often happens due to suspicious activity --- Perhaps nothing on your part. They disable it for no more than Security & Privacy concerns.

Possible Reasons Could Include: 

• Too many unsuccessful login attempts
• VPN (Virtual Private Network) usage
• Consistent transactions
• Session Times Out
• Disobeying Terms & Conditions

So...

To Re-Enable it:

As you might suspect, no one here would know the reason for this occurrence, of course. So, contact Apple Support. They’ll know why this occurred and will run you right through the fix.

Contact Apple Support:

• Contact Us - Choose Locations
• Proceed from there as necessary

Note: Phone calls are taking a bit to go through at the moment, due do lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through :)

sccatke Said:

"My iphone 11 pro connecting Wifi and mobile network become very slow: As title above,its wifi and mobile network connecting is become very slow and reset all setting already but still can't solve this problem .It is not the wifi problem since my laptop connecting wifi is work perfectly.[...]"

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Try Removing Of Data from the iPhone itself...

Troubleshooting iPhone Storage:

Internal storage cannot be upgraded. It is what it is. So, the maximum internal storage capacity never increases, even if you upgraded your iCloud plan. Learn More here: What's the Difference Between Device Storage and iCloud Storage? Apple Support. 

So, what to do:

Clear Space:

Try clearing internal storage though use of the following:

What Space to Clear:

A. Clear Temporary Internet Files:

Clear your Temporary Internet Files(Cookies & Cache) of Safari:

• Cookies perform remembrance of certain site-entered data.
• Cache keeps a snapshot of the last time you visited a site.
• Go Here: Clear the History and Cookies from Safari on your iPhone, iPad, or iPod Touch - Apple Support

And...



B. Clean TV and Music Libraries:

Remove all unneeded files from your TV and Music Libraries. Full-Movies take up 2-4GB typically, and a bunch of those would take up a load of storage, ideally. So, if you have any movies that are not needed, then delete them.

And...

C. "Other" being the Culprit:

Use this Link: How to Check the Storage on your iPhone, iPad, and iPod touch - Apple Support. The storage named "Other" is the grey bar. So, to clear that, this is what to perform: Clear Other storage on your iPhone or iPad - Apple Support

For more, see my following reply.