There is nothing wrong with questioning God, especially when it comes to the loved ones we have lost. I personally believe God provides the answers, but only to those who "have ears to hear and eyes to see" as written in Mat 11:15 and various other places in the Scriptures. However, you might be very surprised to learn how that not many at all have ears to hear and eyes to see, in part because they do not believe the Scriptures. So because the many do not believe the Scriptures, they tend to make up their own beliefs which lead to divisions.
Having said all of that, the Scriptures are very clear as to what happens when a person dies. It's very simple and even a child can understand, but you gotta believe it.
Ecc 9:5 The living are conscious that death will come to them, but the dead are not conscious of anything, and they no longer have a reward, because there is no memory of them.
Notice how "the living" having a consciousness is contrasted to "the dead" being unconscious. People who are alive are aware that they will die because they are conscious and still able to think (usually), but people who are dead are unaware of anything because they are unconscious. There is a second witness to support this.
Ecc 9:10 Whatsoever thy hand findeth to do, do it with thy might; for there is no work, nor device, nor knowledge, nor wisdom, in the grave, whither thou goest.
And a third witness.
Psa 146:4 His breath goeth forth, he returneth to his earth (unto dust shalt thou return-Gen_3:19); in that very day his thoughts perish.
So contrary to popular belief when a person dies they are really dead and not really alive in another location such as Heaven or Hell. But this isn't the end of a person as Jesus promises a coming Resurrection of the dead. It's a promise you can bank on which guarantees that you will no doubt see your father again.
One of my favorite promises found in the Scriptures is one my grandmother read to me as a child to comfort me. A child who's mother was murdered and taken away too early. May it comfort you as well.
Isa_25:8 He will swallow up death in victory; and the Lord GOD will wipe away tears from off ALL FACES; and the rebuke of his people shall he take away from off all the earth: for the LORD hath spoken it.
Rev 21:4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
I want to share this study paper with you which has helped me immensly with putting my mind at ease concerning my loved ones. The writer of the paper expounds on the idea that the dead are really dead as it's written in the Scriptures.
https://bible-truths.com/death.htm - AN ENCOURAGING THOUGHT ABOUT DEATH
Peace and God bless you argkangie and my sincere condolences to you for the loss of your sister and father.