My site is extremely slow even after using smush

Handrail ur is a UK company that guessed it ...handrails....they desire that their users can make their purchase online by a series of steps from type of glass, shape, style etc etc...these steps have been actioned via gravity forms....the final output of these steps is a 3d model of what the users handrail will appear like (roughly)...We have made a tone of savings with smush and again on a smush (we forgot to include original images). We may need to smush again but honestly, I would not say this is the issue as it has not improved the load time...circa 15 seconds...I believe the issue is that gravity forms are loading all potential outputs (which is 1000s) at the beginning instead of at the required step meaning the site takes an age to load if the page indeed loads at all.