You provide very little background information. It is therefore difficult to understand what exactly you want. In addition, there is very little sample data in your database.
I suspect that you will have to write a query for each question.
Question 1
Code:
SELECT tbl_clients.Nom, tbl_clients.Prénom, tbl_forfaits.Début_val, tbl_forfaits.Fin_val, tbl_forfaits.Articles
FROM tbl_clients INNER JOIN tbl_forfaits ON tbl_clients.tbl_clients_N° = tbl_forfaits.lien
WHERE (((tbl_forfaits.Fin_val)>=Date()));
Question 2
Code:
SELECT tbl_clients.Nom, tbl_clients.Prénom, tbl_forfaits.Début_val, tbl_forfaits.Fin_val, tbl_forfaits.Articles
FROM tbl_clients INNER JOIN tbl_forfaits ON tbl_clients.tbl_clients_N° = tbl_forfaits.lien
WHERE (((tbl_forfaits.Fin_val)<Date()));
Question 3
Code:
SELECT tbl_clients.Nom, tbl_clients.Prénom, tbl_forfaits.Début_val, tbl_forfaits.Fin_val, tbl_forfaits.Articles
FROM tbl_clients INNER JOIN tbl_forfaits ON tbl_clients.tbl_clients_N° = tbl_forfaits.lien
WHERE ((([Fin_val]-Date())=5));
Question 4
Code:
SELECT Articles.Aticles, Count(tbl_forfaits.tbl_forfait_N°) AS NombreFROM Articles LEFT JOIN tbl_forfaits ON Articles.Aticles = tbl_forfaits.Articles
GROUP BY Articles.Aticles;