IF a black hole collides with a star or other massive object, then obviously, the resulting object is more massive than the original black hole, so it would have a "growth spurt" (I made that up). So, technically, they do "suck stuff in" and "grow" but it's not like they're the Hoovers of the universe.
So far, every galaxy observed (lol only 1, the Milky Way) has a super-massive black hole at its center.
what would happen if two galaxies collided, would the super massive black holes collide at such high force combined with all the material circling them to also then get sucked in cause the big bang. or would the mass that is circling the original black holes help to influence the resulting spread of matter in the explosion