Boolean union doesn't work properly how do i fix it>

I want to boolean these parts but when i do it creates a mess.
file is too big to upload thats why im posting images

If what is in the second image is what is left after an attempted BooleanUnion, I suspect your part(s) is(are) not closed and is perhaps “inside-out” (just a theory without the file). Select one of your parts and look in Properties to see.

Thanks a lot mate, Cheers!