Thank you very much for your help, really.

I can now crop it as I want, but when it is displayed on the profile, it is still square and not the cropped image in a rectangle.Could you tell me why?

By default, Elgg config has these sizes for avatars:

'icon_sizes' => [
   'topbar' => ['w' => 16, 'h' => 16, 'square' => true, 'upscale' => true],
   'tiny' => ['w' => 25, 'h' => 25, 'square' => true, 'upscale' => true],
   'small' => ['w' => 40, 'h' => 40, 'square' => true, 'upscale' => true],
   'medium' => ['w' => 100, 'h' => 100, 'square' => true, 'upscale' => true],
   'large' => ['w' => 200, 'h' => 200, 'square' => true, 'upscale' => true],
   'master' => ['w' => 10240, 'h' => 10240, 'square' => false, 'upscale' => false, 'crop' => false],
],

You can override this config via custom plugin.

Use My plugin again.

1 - Open elgg-plugin.php and add this code before last ];

'events' => [
    'entity:icon:sizes' => [
        'group' => [
           \MyPlugin\SetIconSizes::class => [],
        ],
   
        'user' => [
          \MyPlugin\SetIconSizes::class => [],
        ],
      ],
],

Without code it's difficult to understand what's happening.

No code means no help.

If the code is large, place it on GitHub, GitLab and publish the link here so other developers can see your project.

Also one of the common development pitfalls is caching. Make sure eighter caching is disabled or after you create a new view, class or add a language string invalidate the cache.

No code - no help. Deploy your plugin on GitHub and we'll see how we can help you

@rivervanrain Please check this link https://safalaya.com/mod/meet.php to see if my Plugin is working properly . Code is ok 

Code is ok 

Ah, ok )