There are architects who often do not consider the building as a whole concept.
This applies to " warns" architects often, and to "architects" even more often. But that does not mean it would be good to make the planning a matter for amateurs to take charge of.
It is also very difficult to simultaneously pay attention to interior and exterior and the related detailed planning.
I also strongly and urgently advise against wanting to do a one-stage all-in-one planning, in which the stages preliminary draft, draft, and detailed planning are attempted to be done in a single 3D color drawing. Unfortunately, the popular clicky-colorful 3D simulation software invites this (or at least does not admonish to refrain). However, it is a balancing act that professional planners avoid for good reason. A preliminary draft cannot only be scribbled, it should be. At this stage, it is only about visualizing the evidence that the conceptual idea translated into a massing arrangement can be a viable calculation. Anyone who already refines details at this point better resign themselves to enmity. That is precisely the difference between wanting to imitate the working method of a real professional or a real novice.
You forgot a word. The "lassen" after "überarbeiten". If such a draft with such an exterior view comes from a layman, one better advises to go to an architect.
But preferably more gently than the OP here experienced.