Hi Arjan Gelderblom,
Modeling is certainly a product of several skills and knowledge. What is easy for one might be difficult for another artist. Your question has no right or wrong answer.
The front element looks like a Lathe based part with a part later on cut out, then welded to the long straight parts. Create a profile (spline) from that shape and place it into a Lathe, make it editable, then use a Spline to cut out the area so the cylindrical load can be placed. Where the cut is, some repair is certainly needed.
Your method to get very close with a Primitive is often a good idea, if any “selection” option is known, as well how to store those to get them back quickly. You can see in many posts here that I often add more options later on to a thread, to support that variation idea.
I typically suggest to get the part and photograph it with the longest lens one can get. In this way, a more (or nearly) orthogonal view is given. There are 500mm mirror lenses for a very low price available, even used. They are perfect for occasional work like that. Otherwise, it needs to be measured and guides or splines need to support your work.
A little bit more detailed:
What I found to be true over the years is, that modeling is more like chess, one need to think many steps ahead to win the game. Being prepared, as in drawings (i.e., guides) and pre-visualize the steps is key. Often the easiest first steps are done quickly, only to find out that the amount of information produced is hard to handle, shape or form wise. Here is the base to know all tools as much as possible, to get an idea what works all the way, and not provide a quick initial result. This is based on experience. Information is not knowledge, knowledge is not wisdom, wisdom is not creativity. Knowledge is not gained by watching tutorials, one gains information. Knowledge is gained by doing, creating experience.
Having said that, all tutorials in the world will not be able to give you for each and every problem a solution. IF you get stuck with something, open a new scene file and focus on that part of the scene alone. Often less information in the object, aka points or vertices, allows for a faster change. Starting with a cube and SubSurfaceDivision might from time to time much better than a Lathe or an Extrude. Sometimes the opposite is the case.
With this little excursion done, I would suggest to check which tutorials your haven’t watched so far, and go along with your main problem in mind.
This series might seem way below your current skill set, but that is not the point, the reminder/refresher with the current problem is the key here.
Modeling starts by looking at all things around you, and ask your self, which tool was used, which one would fit in Cinema 4D for that. This is a training that can be done everywhere.
All the best