Hi Anis

You really need a step file, I couldn't do much with it even with messing around with tolerances in rhino. You can see the unjoined edges here over 600 of them out of 6000 or so edges overall so a load of work to recreate. There are some very small sliver surfaces in there which are not nice. You could rebuild these areas but its not fast work. you will spend a lot of time sorting it out a new file will save so much time.

Out of interest what software do they use to create this?

regards

Jamie