Make a page looking more professional

Hi Christophe (CSA75FR ), first for the form, the theme used in the form or the background image doesn't get applied when you use the Forms web part so you are limited to using one of the  background colours for the section on the page. 

Second for the list, with SharePoint Online in the modern experience you can't add custom CSS, but you can add custom column or view formatting with JSON to make the list look better. For example the images below are examples of JSON code I have added to my lists.

The random country below is selected by a flow in Power Automate and displays the list item formatted with JSON. It has links taking the user to a Wikipedia page about the country and a Bing Maps map of the country:

The list below has alternating colours and the JSON also converts the Harvested column from a number into a pie chart:

The list below shows responses to a survey done with Forms. The JSON column formatting colour-codes each item automatically based on the answer to the question:

So it seems to me that you can make a big improvement by using JSON formatting. It's not always easy to work with but there are good examples at https://github.com/pnp/sp-dev-list-formatting/tree/master/column-samples and https://github.com/pnp/sp-dev-list-formatting/tree/master/view-samples

I'll do a mockup of how your list and form could look and post it here shortly.

Rob
Los Gallardos
Microsoft Power Automate Community Super User