Theres a few curves you did alright to be able to win the trophy, all in all id say your error are:
1. You brake too early in some area.
2. You keep the inside before entenring a curve, missing the apex.''outside-inside-outside''
3. You push too much too early and end up sliding just before exiting a corner, make you lose a good amount of time.
For example at the Hatzenbach , theres a serie of curves,the entry was good, the speed was correct and the line was good but at the end you picked up too much speed and ended sliding the car on the last exit. Try going a little slower before the last curve so you can accelerate full throttle without sliding but still using all the track at that area.
Try to use the weight of the car without making it slide too much... hard to describe...
Some curves will have better grip if you make sure to stay inside as close as possible to the cobblestone without touching it... (still keeping in mind the ''outside-inside-outside''...
Like the Ex-Muhle, you steered slightly too late, the car will grip more if you keep it closer to the cobblestone at the apex. and it can make a good difference especially since its going uphill afterward...right there you can gain at least 0.5 second.
On the first part of the track you steered quickly to make the car slide into the corner, but you will keep more speed if you slow down slightly before the curve and just move as close to the inside as possible without touching the cobblestone and exiting very close to the grass on the left, touching the cobblestone(unless you run half the car over it) will throw the car to the outside a little...
Hope that help... but next time post on the GTR trophy thread it will be even more suited.
With more practice you will improve your time.
Anyways, an absolute pleasure to drive. Really heavy steering on the G27, but can take many corners flat. Suspension, Aero and Brake bias tuning 
