Is there any ways to help speed up the assembly process when building big LEGO Technic set such as the 42043 Mercedes-Benz Arocs?
Despite what it superficially looks like in (for example) Sariel's build videos, having a big pile of parts spread across the table is not the fastest way. Pour the contents of the smaller bags into containers (I use old plastic take-away containers). That way you are looking through a container of blue 3 long pins and red 2-long axles for a 2-long axle, rather than rummaging through a mound of everything. I tend to pour the black 2-long connector pins onto the build space because there are so many and that way they're close to the build, but everything else goes in a container.
A little time sorting will help a lot. Sort things like beams and large parts, but also axles if there's a lot of them. Having a row of beams sorted by size and getting a 9 long one is much faster and easier than rummaging and comparing randomly grabbed beams for length.
I find pulling out really large parts early makes things easier. Wheels/tyres, power functions, large panels etc. A stack of 5x11 panels is easier to deal with than when they're randomly in a container hiding little parts underneath them.
I find piling the parts to be used in a step up, then installing them avoids missing any. If you need to add 3 axles, but you have one left over at the "end" of that step... you missed one. This is less necessary with modern kits because you put so few parts in per step, but still occasionally helps. If you look at instructions for pre-2000 sets there's often 10 or more parts installed per step, which made this technique much more useful/necessary.
skim the online forums for build errata and common mistakes. For example, there were quite a number of people asking "the back wheels on my crawler turn one way, the ones on the front turn the other way" because they had mis-assembled one of the differentials. There's also a mistake possible in the core of the more recent wheeled loader, but the detail escapes me.
test mechanisms early and often. Spin every axle, make sure that it does spin and whatever the gears on it seem likely to mesh with, do.
read ahead. If you have an idea of what you're building you can often do things like making two mirrored sub-assemblies at the same time. But be careful, as you can easily end up building the wrong thing.
I build on a towel, rather than straight on the table. That way if I drop a pin or something small it doesn't bounce as much. Specifically, it doesn't end up on the floor under my desk.
have enough space. The days when you could build a set "in the box" just by opening the lid (or these days, cutting round the top) are gone. A towel is not a bad estimate of the space required for building something like the Arocs.
(the build videos are usually made by experienced builders who have excellent spatial memory, and they get things out without disturbing it, so parts stay more or less separated by bag despite being "in a pile". If you look for this it's often obvious. Especially If you're building with kids you'll generally have to struggle not to rummage until the pile is completely randomised)