I would like to display in a loop a div class one time in two (Symfony)

i'm working on a personal project and i want to do this :

https://i.stack.imgur.com/wC4f0.png

So there is my code with a loop who work well :

On my page it look like this :

https://i.stack.imgur.com/PGjv4.png

How to alternate the display in my loop please? I work with Symfony.

I hope you will understand my english.

Have a good day !