I would look for where three seems cross. if you find that case, spin the ball so the seem of it is away from the crossed seem in the handle. that would be how I narrow things down.

Hi Bence, here's a version with the booleans completed.

I scaled it up by 10x in size and sort of un-striped it by using Boolean Union on pieces that had been cut from the same original surface and used Construct > Network to build this area:



Then booleans went ok after that.

- Michael

Michael,you are a magician, I still have to learn a lot I see, kind of a beginner, thank you <3