Issue with relationships

Hi All, 

Apologies if the question has already been asked and solved, but I'm fairly new to Power BI and when it gets too technical I just don't understand the answer so thought I'd rather post it again with my specific issue! 

So I somehow manage to create a dashboard to display revenue achievements from our CRM database (OData). Our CRM does not deal with target per consultants, so I had to create a spreadsheet that where we can input the monhtly target per consultant. 

After testing many displays, this is how I organised my spreadsheet: 1 column for username, 1 column for the date, and the last one with monthly target, as per below:

Here is what I want to achieve:

Create a graph that shows monthly achievements taken from our CRM data (which works); and show the line that should be the target we needed to achieve initially, taken from my spreadsheet. I manually set up a filter so that it shows the target in 'this month' otherwise it would show me the yearly one. 

I think the issue comes from the fact that I can't associate my sheet's columns to the CRM ones. I tried to manage relationships manually and it automatically picks up the username as being the same one from the CRM, but when I want to link the target month with the date the deal has been created on, I get the below error:

I read something on the forum talking about a measure with userelationship or something but didn't really understand how that works and what I should do really... If someone could please advise?

Many thanks in advance!