how i can get skype

If one upGrades the version of OS X or macOS to something Skype is supported on then maybe it will work

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence.

Computer Qualify for the Monterey upgrade

macOS Big Sur 11 hardware requirements

macOS Catalina 10.15 hardware requirements

macOS Mojave 10.14 hardware requirements

macOS High Sierra 10.13 hardware requirements

macOS Sierra 10.12 hardware requirements

OS X El Capitan - Technical Specifications

Caution - jumping over all the newer versions and directly to Big Sur  / Monterey on Qualifying computers is Technically possible - there are those who have attempted and were successful. Then there are those who attempted and had less than good results.

If this is a Production or Mission Critical Set-up - a more prudent and measure approach is suggested. 

The above is from observations on the Apple Support Community Forums and IMHO

Tips Big Sir Upgrade Released Nov 2020

Tips Monterey Upgrade  Released Oct 25, 2021

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur & Monterey supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal  operation of the OS and may even Corrupt the OS requiring a Reinstallation

Why pursue the Skype issue.

As in your other posting https://discussions.apple.com/thread/253627922 is appeared one was interested in a newer version of OS X or macOS what might be able to run a newer version of Skype.

ArazPoury wrote:

but why it dont sign in on a old version? from 2016

Because Microsoft has dropped support for that version and will not permit it to connect.

The two are related and same answer

https://discussions.apple.com/thread/253634960

I found several web sites with older versions.

This looked the most promising.

SKAIP.org

They had a version released in 2016 for the Mac OS

You can't.

Microsoft no longer allows it.

Ask Microsoft. That is not an Apple product or service. This has nothing to do with Apple.

Sorry, but getting any software other from Direct from Developer of this software is a risky business.

What is included maybe more than what is expected and bundled with Malware or Adware.