@vgeorgievK7586 - If you are able to share the design, it will be easier to give advice. But, a few things you might look at: Do the machines have more detail than you need (every fastener, with modeled threads, internal details of gearing, etc)? I find that you need to understand your goals with every model. If you are designing the machines themselves, down to that level of detail, then perhaps such detail is needed. But, if, instead, you are, say, designing a station where some machines are being installed, then, perhaps a simplified representation of a machine would suffice.
Also, it would be good to know, for this design, exactly what operations are too slow. You mention 2D drawings, but what other operations are you struggling with? Adding new joints? Adding components? Sketching? Solid modeling? Editing a feature and recomputing?
Jeff Strater
Engineering Director