Hi @Roberto_Zambrano,
welcome to eazyBI community! 
You can create a report by using Assignee dimension in the rows, with this you will get original estimates per assignee.
After that you can find the same user as Assignee from the Logged by dimension with GetMemberByKey() function and display their Hours spent with the following formula:
(
[Measures].[Hours spent],
[Logged by].[User].GetMemberByKey(
[Assignee].CurrentMember.Key
)
)
The report would look like this:
best,
Gerda // support@eazybi.com