Hello Gabriele! This work is beautiful! Is it all from imagination? I'll try to help answer your question, though, if I can. And I've attached some examples. For me, at least, a front view of a tiger's head simplifies into two overlapping triangles at the most basic flat-shape level. One large one for the mass of the head and "cheek" fur, and another for the muzzle, both ending in the same plane on the bottom. The small triangle originates more or less in the center of the larger one. Then I connect the muzzle with the location of the eyes via an upside-down heart that goes into an hourglass shape, ending with ovals. The rest of the head can then be filled out as more or less another upside-down heart. Stick on some ears (ovals), a nose (a triangle), and another little rectangle at the bottom of the muzzle's heart shape for the bottom jaw. If the mouth is open, the smaller muzzle triangle can be extended beyond the bottom of the head triangle. Three-dimensionally, in order to use this to maintain perspective for imaginative drawing, you might try a cone. Or overlapping a cone and a rectangle? It might be worth tracing over a bunch of references from different perspectives, experimenting with these shapes to see what feels best for you. Then you can settle on a primitive form to apply to your imagination work. Just a thought, anyway. Hope that helps!

I leave here the artwod feedback tool link for this drawing... I checked the rules and i didn't get if it's ok... if it's not I'll delete it. https://artwod.com/feedback-tool/c/animals/6a686eae6f4499eb28996141/tigre-che-guarda-lorizzonte