Good morning Naama,
You can space the lines by adding the \n before each line:
const body = `
\nNom: ${$w("#Nom").value}
\nPrénom: ${$w("#Prenom").value}
\nTéléphone: ${$w("#Telephone").value}
\nEmail: ${$w("#Email").value}
\nMessage: ${$w("#Message").value}
\n${intrests}`;
Glad I was able to help.
Yisrael