Hello Frédéric,

Thanks for reaching out to us.

Please, find the answers below

How can I classify the families of massages and the different types of massage as I wish

All services can be edited in the backend of Amelia by clicking of Services tab. There you can see the option to create categories and then assign services to those categories. Those categories will be visible on the booking form (exactly like on your website). I recommend checking out this article to find more information how they work.

How can I change the logo (party favors and hat) present at the end of the payment procedure?

Unfortunately, there is currently no such option with Amelia's built-in features, but you can hide it with the custom CSS code. Please feel free to search through our feature suggestion page,  to see if someone may have already suggested this feature. If you can't see it, feel free to add your suggestion there, and as more people vote, the feature will move higher on the priority list.

Can we enlarge the size of the reservation module in order to read all of the different massage families?

This can be also customized with the custom CSS code, but there is a workaround to display all the information regarding the service/ category name

You can use this CSS code

.am-adv-select__popper .am-adv-select__item-label { 
white-space: wrap;}

Custom code needs to be applied to the page where the booking form is. Depending on what you're using (Gutenberg blocks, or some page builder), adding the CSS or JS can be done in a few different ways. 

If you need help with adding custom CSS to the page, please take a look at this article.

I hope i cleared a bit.