Newbie Driver Mercedes Actros Low Power on Hills

Hi there,
I am new to trucking with tractor/prime mover and trailer combo.
my brother has just bought a 2009 2644 Actros prime mover and a drop deck trailer. He is half way home on a 1600Km trip. He has reported to me that he is loosing power on hills. The trailer (9.5T) is unladen and he feels a truck with 440Hp should climb these hills with ease. He is being overtaken by all other vehicles.
He is wondering if he has something set wrong on the dashboard. Power/economy?? He is tonight trying to read the manual some more while having a 9 hour rest sleep stop.
I thought I would ask people with experience to give some suggestions. I told my brother maybe the engine is stuffed...? I hope not.

Thank you for any replies.

 

I am sorry, but I don't understand your reply.

 

Thanks guys for your comments so far.
We are located in Australia. I have passed your suggestions onto my brother this morning.
I think there is little he can do until he gets this rig back home so we can check it out if what you have said could be the problem.
This truck was one of 5 traded in at a Merc dealership. Apparently four resold in no time, however, this one stood there for almost 2 years? Until we came along.The Merc dealer spent a lot ($9K)on fixing small items such as bulbs, seat belt, paint job, service etc more than a year ago while it was on the lot. So, it has been standing for around two years. It has a large remote control Hiab on the rear which is perfect for our needs. We bought a brand new drop deck extendable trailer with removable hydraulic ramps. All kitted out with container pins and pedestals. She can carry upto 1 x 20 foot plus 1x 40 foot container if needed.
This combo just ticks so many boxes for our various needs. We don't intend to do long hauls, just a 250Km radius from our business.
We have one other vehicle (Australian made) with a Merc engine. But other than that, we are new to this fully European truck.
Thanks again. I will update you when I know more.
Forums are such a great wealth of knowledge.