Issue with my macbook pro

"how can i update from OS X 10.11 to OS X 11 version"

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For reference...

Upgrading the macOS:

Determining which macOS Upgrades(s) will Install:

I. Verify Compatibility:

A. Start Here: Learn About Compatibility and how to Identify your Specific Mac Model - Apple Support

B. How to Verify:

I Reveal your Model:

What is the Model of your Mac? To find out...

1. Go to: Apple menu
2. Click: About this Mac
3. View: Second Line-Down

then...

II. Compare the Results:

See if the Model you found is shown here:

• macOS Ventura is Compatible with these Computers - Apple Support
• macOS Monterey is Compatible with these Computers - Apple Support
• macOS Big Sur 11 Hardware Requirements - Apple Support
• macOS Catalina 10.15 - Hardware Requirements - Apple Support
• macOS Mojave 10.14 - Hardware Requirements - Apple Support
• macOS High Sierra 10.13 - Hardware Requirements - Apple Support
• macOS Sierra 10.12 - Hardware Requirements - Apple Support
• OS X El Capitan 10.11 - Hardware Requirements - Apple Support
• OS X Yosemite 10.10 - Hardware Requirements - Apple Support

III. If Compatible:

Back Up your Mac First:  Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.

It helps us to know the exact model of your laptop since not all laptops can be upgraded to macOS 11.x Big Sur. You can get the exact model by clicking the Apple menu and selecting "About This Mac".

Generally only 2015 - 2020 models are compatible with macOS 11.x Big Sur.

How are you trying to download apps? Which apps? Most apps within the Apple App Store probably are no longer compatible with macOS 10.11 El Capitan. Most likely you will only be able to download older previously purchased apps from the "Previous Purchases" section of the App Store.

If you are trying to download items from a website, then Safari is likely too old & out of date to work with most websites today since a lot of new security features have been added to websites since that old version of Safari was released. You may be able to download items from websites by using a third party browser, but most third party browsers no longer support macOS 10.11 El Capitan. You may be able to find an older version of a third party browser which is compatible with macOS 10.11 which may still be able to access some websites, or you may be able to find a browser which has been backported to work with macOS 10.11 (be careful of this option though).

Make sure macOS 10.11 is fully patched & updated. You may want to try booting into Safe Mode to see if that makes any difference. If Safe Mode works, then it most likely means you have some third party software installed which is interfering with the normal operation of macOS. Usual culprits are anti-virus apps, cleaning/optimizer apps, and third party security software (including VPNs)....none of which are needed on a Mac.

It is possible you may first need to install macOS 10.13 before being able to upgrade to macOS 11.x Big Sur since the macOS 10.13 installer has a system firmware update which is required for using the APFS file system required by later versions of macOS (theoretically the Big Sur installer should be able to update the system firmware, but I have seen later macOS installers have some weirdness if things are not as they expect....like being so far out of date on the OS & firmware.

I highly recommend you create a bootable macOS 10.13 and 11.x USB installer so that you have more options if something goes wrong during the upgrade process. At the very least a macOS 10.13 USB installer.

Create a bootable installer for macOS - Apple Support

You also definitely want to have a good backup of your computer before you even attempt to upgrade macOS just in case something goes wrong and you lose access to the data on the boot drive. People should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data.