What is the main problem of the transition from chemical to biological evolution?

According to the laws of evolution, complex forms appeared after less complex ones. First, protons, neutrons and electrons appeared, then chemical elements, then complex molecules. So it is in the biological form – first eukaryotes, then prokaryotes, first unicellular forms, then multicellular ones appeared. The new could not arise without the old, without the simple. The new created the conditions under which the previous forms either disappeared or were transformed. The problem of the transition was the emergence of the genetic code and self-reproducing cells.