Ok. So the Duncan Mosquito has a take apart design. It works for the first 10 times and after that i tried taking it apart and it wont unscrew from the bolt. WTH? any ideas or help ?
You must have overtightened it and now it’s in bad shape. Not sure what to do other than buy a new one.
as Icthus said you may have over tightened the halves togther and have stripped the axle or you may have cross threaded the halves together, either ways just go get a new one there cheep as chips.
Literally.
Same thing happened to my first mosquito after a month or so. The plastic of the small cylindrical housing around the bolt end of the axle (visible when you unscrew the sides) bent after continuously doing harder throws (trying to make it spin longer than 30sec :-X). At that point it would’nt tighten much at all then finally that part of the axel split in half, requiring me to crush that side with pliers to remove the axle because at that point I could’nt even unscrew it! So yeah, get a new one, and be gentle on the throws 
better yet return or exchange it. you will save $5 vs. buying a new one. 
I dont think thats right; one thing is that the yoyo came with problems out of the box, and another is that
you ruined the axle and the yoyo was without problems.
same happened to me my first was a speed beetle years ago …after hitting the floor a hundred times or so the plastic part that holds the bolt in place so you can put it togther finally broke…I tried glueing it back together but ended up over tightining it ruind it completely
A. The axle is worn out from OPENING THE YOYO AND CLOSING 2 MUCH
B. Throws 2 hard
C. I don’t know