Hi,
great plan to start a project.

I would help to design (Solid Works Student Version). But i cant build many prototypes, because Im student and havent much money

At least i would say we need a auger drill bit for transport from hopper to extruder (or want to make a gravity transport?). And we need a heater, easiest Way a 50W resistor. I would check temps with a Arduino, because I have a Arduino anyway. And we need a precise nozzle with 1,75mm(3mm)and the feed tube between nozzle and heater. Maybe it should be a turning part.

Auger drill bit 8$
50W resistor 3$

cu Ole