I figured it out. Thanks Demoneyejin for offering help. I fought my way through it solo in end though.
I still have a problem and that is with precision.
If a Projectile flies like in image:
Then corresponding tile I get, is empty one above tile it impacted.
only way to do it I see is to do a raycast against last ticks position and see which tile is in way. Seems like a rather expensive check. Any better ideas?