School challenge Cabine with no chance to demension

Dear Cad users ,

I have recived a new task for my engineering study. Its about drawing  a truck cabine in inventor , it shoud be as detailed as posseble.
I only got 1 autoCAD drawing , the problem is all the curves are drawn in short line pieces. I suggest this is a very old drawing , i can't import it into my inventor ore even demension it in autocad. I know the Max measures but still its hard to gamble all those curves and lines togetter.

So my question , is there a way to fix this? so all the small lines become a curve so i can measure them and draw an exact copy into my inventor? 

I attach the file to my post so you can look into it and understand my problem .

Tnx allready for your time!

Greetings ,

Daan