Easy Profile - Joomla Extension

Hi,
sorry for late reply, it was weekend for us

Actually I cannot understand how "Filter database options based on the value of this field" and "Choose a column where will be applied a filter" wprks

I try to exaplain you with an example:
when you use DB options then the options will comes from a DB table with a query like

SELECT value,title FROM table

with "Filter database options based on the value of this field" and "Choose a column where will be applied a filter" the query will become something like this

SELECT value,title FROM table WHERE column = another_field_value

"column" was set by parameter "Choose a column where will be applied a filter" and "another_field_value" is the value of the chosen field in parameter "Filter database options based on the value of this field".

Example:
I have 2 fields:
Field 1: called "Country" width these options

it|Italy
fr|French

Field 2: this is select that load all city from a table like this:

id    name    country_code
1    Paris    fr
2    Cannes    fr
3    Rome    it
4 Milan    it

I set field 2 with following parameters:
Table: cities
Column for value: id
Column for Text: name
Filter database options based on the value of this field: Country
Choose a column where will be applied a filter: country_code

Now the options in the field 2 will change based on value of a field 1....for example if I choose Italy in field 1 then I will have only italian cities available in field 2

I want a drop down with users (I understand how I can select the users) of the site but only the users based on other profile filed (fore example only male users)

this is not fully possible, because the data of users are stored in 2 tables: Joomla user table that contain names and Easy Profile table that contain gender. So if you will make something like this then you can select only lastname or firstname as Text Column (but not formatted name).
Anyway your question is not clear, what mean "based on other profile filed (fore example only male users)",you have a field called gender and you want to select users with the same gender?