Hi Damien,
Thank you for your inquire.

1. Yes this can be done using shortcodes.

for example

[ameliabooking employee=1] if you want to show the booking form for the employee with ID 1,

[ameliabooking category=1 employee=1] if you want to show only the services from a category with ID 1 that are assigned to the employee with ID 1,

[ameliacatalog employee=1] if you want to show the services of one specific employee with ID 1,

2.

Unfortunately this is not possible at the moment, the language that you choose in the WordPress settings are the only one that can be used at the moment.

Best regards.