Some apps which are in my phone hidden

There are a number of apps that are installed as part of iOS. Some of them can be removed and some can't.

See here:

Remove built-in Apple apps from the Home Screen on your iOS 10 device or Apple Watch – Apple Support (UK)

Anything not installed by Apple was installed by someone. Do you share an Apple ID with anyone? Has anyone had access to your phone while it was unlocked?

To ease any concerns you may have, you do have the option to factory reset your phone. Before you do this you should also change your Apple ID Password. There are a few things that you would want to check before a factory reset to insure you do not lose any data that you want to keep.

• Are you using iCloud Photos? If you are, then the photos would not be removed with a factory reset. If not, you would want to save those photos in another location to avoid data loss.
• Are your Contacts saved to iCloud?
• Do you have game data stored on your phone, such as game levels that you want to keep?

By doing the Factory reset, the phone will be wiped and you can set it up as new. To avoid having the apps that you do not want back on your phone, you will not want to restore from a backup. Anything saved in iCloud will not be lost. If you are concerned about losing any specific data not mentioned before doing a factory reset, then ask here first.

Update your Apple ID password - Apple Support

How to factory reset your iPhone, iPad, or iPod touch - Apple Support

This will bring you back to a new phone as long as you do not restore from a previous backup. You should still use your Apple ID when setting up the phone to bring back any data that is stored in your iCloud. Do not install any VPN software. If you have any other questions, ask before you proceed.

Another note, the apps stored in your App Library are not hidden files. That is just where all the apps are stored on your device so you can set up any number of screens to view the apps. Some people will just set up 1 or 2 screens of the most important apps they use and leave the others in the App Library to reduce clutter on your screen.

Feez09 wrote:

i don't even share my apple is with anyone and how does that even happen for them to hidden installed those apps? And I don't even have an Apple Watch . The funny thing is sometimes my phone just asked me to unpair. Which I don't even know how.

You are free to remove many of the preinstalled app on the phone as shown in the link provided by IdrisSeabright.

Is this a phone that you purchased new or a purchased from a third party?

The Watch app can be removed, but if your phone was previously paired to a Watch, it would need to be unpaired first. This would lead me to believe that is was a used phone if you did not ever have a Watch.

Not sure what you mean by hidden apps. All the apps that are on your phone are available in the App Library that is available by swiping all the way to the left. You are free to put any of those apps on any Home Screen you want. You do not have to have all the apps on a Home Screen.