Acceleration of car on a gradient

When the car is on the hill that makes an 8 degree angle with the horizontal, now both gravity and friction is working against the driving force, so its acceleration will be less. What is the component of the gravity force along the incline? What is the net force acting on the car?

 

There is the normal push from the inclined plane, which will be different than for horizontal plane.
So the friction will be slightly different too.
The largest effect comes from the tangential (along the ramp) component of the weight.

 

Forget about force triangles. Choose the x axis as the axis parallel to incline, and the y axis as the axis perpendicular to the incline. Assume friction force is 900 N. Draw free body diagram of car, identify all forces acting, and apply F_net = ma in x direction. Be sure to correctly determine componets of the weight in the chosen x and y directions. See here for a brief tutorial:
http://hyperphysics.phy-astr.gsu.edu/hbase/mincl.html

 

You are making it too complicated. This is not a real situation analysis but a school textbook problem. I agree that it is not clear what kind of friction is the one given and it does not matter for the first part of the problem.
Anyway, even assuming that it is some sort of kinetic friction, you can ignore the change on the ramp because it's second order in the angle whereas the tangential component of the weight is first order.