How can i make an animation like csgo case opening?

I think that is a thing you will not get a really answer on. Such a case opening mechanic like in CS:GO is really complex and involves different types of skillsets : Art, programming, animating etc.

That is not a simple task to do at all.

@Dext isn't wrong @andreistalker. You may well be able to this with some of the elements of the new(ish) UI.

I've done something similar for a 3D menu, I kept a list of inventory items in an array. Each of the items were stored in Resources and I had a list of them in that array.

When I opened the inventory it instantiated the menu objects below the terrain and I had a separate camera slid along the line of objects.

In your case (although I've not played that game - so only going on YT examples) you want something similar but when it gets to the end it starts again. seamlessly from the 1st object.

Now game programming is as much about smoke and mirrors as it is about facts. The game world is not real and it's faster to move the location of an instantiated object than it is to destroy and instantiate it again. So as you head towards the final object in the list move the first one to be just after it and so on.

You'll need some skills and look up rendertexture to display what the camera's seeing (3D objects) in a 2D menu.

Potentially you could have the guns rotating as the camera passes over them with text underneath as well.

Difficult but doable. This is a good place to start