Hi Arnaud,
I would first recommend adjusting the “Default stylesheet used for events templates” and “Events template” settings under Events > Settings > Display. These affect how much events pages inherit their styling from the theme.
If this doesn’t make a difference, then you may need to add some CSS. While we are limited in the amount of support that we can provide for customizations, if you can send me a link to an event where this is happening, I’ll be happy to take a look and see what I can recommend.
Thanks,
Jennifer