How to use the EXEC command - sql

Question

I am trying to get a result from a database that will be selected after knowing the country of a user given his email.
I tried using EXEC() but now I get too many results from different users when I clearly indicate that I only want the result from certain user in the 'where' clause.
I first tried making the query with pure inner joins but it failed, it indicated that there was a syntax error, but if i ran it separately without the exec it worked.
After that I decided to use sub-queries, but as I mentioned above, it is returning all of the values, as if it wasn't considering the 'where'
What am I doing wrong?
Here is a sample of the query:
DECLARE #email nvarchar(150) = 'name.lastname#mx.company.com'
--Getting the country code of user
DECLARE #country_code nvarchar(3) = (SELECT country_code FROM general.countries WHERE id_country = (SELECT fk_country FROM databases_access.staff WHERE email = #email))
--Setting user database to search for job title & department
DECLARE #dbname NVARCHAR(25)
SET #dbname = 'dsv_global_' + #country_code
Declare #query nvarchar(500)
-- Query to be run to to get the user department and job title
SET #query =
'
USE '+#dbname+'
SELECT
id_staff,
email,
(SELECT complete_name_dept FROM dsv_global.departments WHERE id_department = fk_department),
(SELECT CONCAT(title,'' '',description) FROM dsv_global.job_titles WHERE id_job_title = (SELECT fk_title FROM dsv_global.staff_information WHERE fk_staff = id_staff)) ,
(SELECT COUNT(fk_staff) FROM dsv_global.staff_managers WHERE fk_manager = fk_staff)
FROM dsv_global.staff
WHERE email = '''+#email+''' AND status = ''ACTIVE''
'
----Storing department & title from user in temp table
--DECLARE #user_info TABLE (id_staff int, email nvarchar(200),complete_name_dept nvarchar(100), title nvarchar(200),num_of_errors int)
--INSERT INTO #user_info
EXEC(#query)
Edit:
I expect to receive:
But I receive:

Answer 1

It's worth to use Common Table Expressions when you deal with complex queries. You can put WITH to define a temporary named result set that available temporarily in the execution scope of a statement. And, by another hand, put GROUP BY for your COUNT function. Also, you need to put id_staff inside the WITH block, it looks like:
WITH cte_titles ( job_title)
AS (
SELECT CONCAT(title,'' '',description)
FROM dsv_global.job_titles
WHERE id_job_title IN
(SELECT fk_title
FROM dsv_global.staff_information
WHERE fk_staff = id_staff)
),
cte_staff (count_staff) AS
(
SELECT COUNT(fk_staff)
FROM dsv_global.staff_managers
WHERE fk_manager = fk_staff
GROUP BY fk_staff
)
SELECT
dsv.id_staff,
dsv.email,
job_title,
count_staff,
FROM dsv_global.staff dsv
cte_staff,
cte_titles
WHERE email = '''+#email+''' AND status = ''ACTIVE''

Answer 2

The problem is that i was not assigning enough space to store the query inside a string :
I had:
Declare #query nvarchar(500)
i changed it to :
Declare #query nvarchar(500)