The vast majority of the fossils we find on this planet are the result of the catastrophic global flood around 2350 BC, recorded in Genesis 6-8, and memories of which remain throughout the histories and traditions of cultures around the world. The "billions of dead things buried in rock layers laid down by water all over the earth" are a very clear testament to the accuracy of the Biblical narrative, and to the results of human sin and rebellion against God (Genesis 6:5, 6:12, 6:17).
Some people mistakenly believe that 6000 years is not enough time to form a fossil, but this is demonstrably not the case. Indeed, some dinosaur fossils still contain soft tissue! In fact, you can watch the fossilization process yourself over just a few days using materials you may already have in your own home.
Some may argue that these rapid, modern examples are not really fossils, because, by some definitions, fossils are necessarily "prehistoric". If this is the case, though, then no fossils exist at all, since history goes all the way back to the beginning (Genesis 1:1; John 1:1). Generally, most people think of a fossil as simply being a "plant or animal that has turned into rock", and these appear in abundance around the world.
Fossils of creatures are usually formed very quickly, or else the organic material they describe would decompose before completion, leaving nothing to be fossilized. If the environment always worked slowly at fossilization over millions of years on any given corpse, we wouldn't have any animal fossils at all!
A rapid burial in sediment-rich water, such as would be expected in a turbulent global flood matching the Biblical narrative, is the best explanation for the abundance of fossils we find in the earth.
The flood destroyed life on earth because man's sin was terrible in the eyes of God (Genesis 6:5). Since death is the result of sin (Genesis 2:17; Romans 5:12, 6:23), and since all of us sin (Romans 3:23; 1 John 1:8), death is all we should expect. However, our gracious God has not only extended our lives on this earth instead of destroying us immediately, but He has also offered us eternal life through resurrection if we place our lives in the hands of the resurrected Son of God, Jesus (John 3:15, 17:2-3; Romans 6:23).
If you have not committed your life to Christ, recognize that through Jesus Christ God has offered you forgiveness for your crimes and disobedience against Him (Luke 5:24; 1 John 1:9; Acts 13:38). If you turn away from your sins and turn toward Christ, asking for God's forgiveness, you too can receive the forgiveness of God Himself (Acts 2:21, 4:12, 16:31; Romans 10:9, 10:13), and avoid the wrath to come, a wrath by which the great, global flood will pale in comparison (Mark 9:47-48; Luke 13:28; Revelation 14:11).