This should be at lears 6 sketches - one external contour, 3 for the holes that can be linear patterned, one for the longer hole and one for all other holes. There are 474 constraints in that sketch. What number would you consider too much?

Please read the info here http://forum.freecadweb.org/viewtopic.php?f=3&t=2264 and provide necessary info. Also did you try what I suggested in previous post? Will you answer what your craphic card is?

I did not knew that would help later Here we are using mirror to create other supports from the first one. Since the basic shape can be symmetric it is easy to mirror over base planes (XY, XZ, YZ) instead of defining extra planes. So creating the model around the center helps later. I usually used ...

View/Standard views/Fit all fixes it here with same version as yours. It first becomes very small but then when I zoom in there are no more artifacts.

Symmetry for the base sketch for easy placement of later features. Sketches drag/dropped over the body name to place them inside the body. Mapped to base planes for propper attachment. Sketches fully constrained with meaningfull constraints - could be measured in real world. Screw holes connected to...

Do you want help? Then why did you not post in the Help subforum? Could you provide your FreeCAD info as per IMPORTANT link on top of Help subforum? Also what is your graphics card? Could you try with development version FreeCAD_0.19.18234_x64_LP_12.1.2_PY3QT5-WinVS2015.7z from here https://github.c...

Here is something to get you started:
.

Her is a PD tetrahedron with basic dimension edge length:

Feel free to do so but bear in mind that this is mostly English speeking forum so you should try to either translate or post in relevant French subforum. It is not easy to follow multylanguage thread. I for example will not post in French, Google Translate will translate both English and French to B...

Nice I really like CAD to real world projects. Post some pictures of your progress please.