Question: My problem is that I can't get the full width and height, I have tried lots of things but I can't get it right and now I am asking you guys to help me.

<http://i.imgur.com/tjACREv.png>

<http://imgur.com/tjACREv>

What you are seeing here is a picture of my header.

Everything works but I can't remove the background lines at the outide of the image as you can see it: left, right and top

so how do I fix that?

Answer: 
Given that you do not want to use a third party tool then this is not achievable with SSRS.

Assuming end users have some PDF Reader - granted a third party tool, but probably already in use - then is exporting the report in PDF format a suitable alternative?
With SoftArtisans OfficeWriter's SSRS integration, you can create do this by turning on worksheet protection in the template Excel file that is embedded in the RDL when the report is designed with OfficeWriter's client-side designer (an Excel add-in). The output file will be locked and protected. See: [OfficeWriter for SQL Server Reporting Services](http://www.officewriter.com/officewriter-for-sql-server-reporting-services.aspx)

Disclaimer: I work for SoftArtisans, makers of OfficeWriter