Hello Ariane!
Thank you for using Events Calendar Pro. I can help you with this!
It looks like you’re on the right track, to get closer to the layout your referencing you can add some styles to your theme’s custom css file. If you don’t have a custom css file you can download and install this plugin which will add a custom stylesheet for you. https://wordpress.org/plugins/simple-custom-css/
This is the snippet to add:
.tribe-events-list .tribe-events-event-image { width: 30%; }
Let me know how it goes or if you have any further questions!
Cheers,
Trisha