Your logo, http://autonomouscars.com/css/white_...lanilanboy.jpg
, is contained in #top #logo ...
Your robotcar.jpg #hheader-wrapper #hheader.
Those are the two images you want to put side by side?
logo-kullanilanboy.jpg at 609px width
robotcar.jpg at 630px width
.hs-deac at 330px width
makes for a 1569px width... Is that what you're wanting to do?
To make your logo transparent so only the letters show, you would need to photoshop that into a transparent .png