Hi Sun, here are some cutting surfaces that have been simplified as described above.

I have not had a chance yet to test cutting your main piece with these and doing the filleting, but it should have a much better chance of working with these as the side wall cuts instead of the other previous ones.

You should hopefully be able to select these cutting pieces, then do a Transform > Array > Circular to replicate them, then select your base ring solid (when it was plain without any cuts in it yet), and also these pieces and do a Boolean Merge operation to do all the cutting.

- Michael