how to get the location long and lat out of the raw measurements?
I only know the vastly simplified form: all satellite nav systems work by the satellites telling you where they are and what time it is.  In GPS terms, that time is the "pseudorange", and it's all you need (in theory) to locate yourself.

With no satellites in view, you have no clue where or when you are.  With one satellite in view, you can place yourself on a 3-sphere* in time and space**.  With two satellites you can place yourself on a 2-sphere, etc.  When you have four satellites in view you can locate yourself to a point, and you're done***.

I suggest you look around and get a book on satellite navigation.  I'd love to recommend one, but first, I'm not current, and second, StackExchange discourages product recommendations.  But they're out there, and these days there should be one that covers GPS, GNSS and Galileo.

* I'm using the mathematical terminology here: a 3-sphere is the locus of points equidistant from a point in 4-dimensional space, a 2-sphere is the surface of a ball in 3-D space, a circle on a plane is a 1-sphere, and a point is a 0-sphere.

**  I.e., you know that if it's the same time as the satellite's time you're at the satellite's position, if it's 1ms of a second after the satellite's time you're on a 2-sphere 300,000 meters in diameter around the satellite's position, etc.

*** Except for noise, of course, and I can't recall if, even in the perfect case, you end up with just one possible location or a finite number of them.