I want to know the basic difference between these three subjects: Microbiology, Biochemistry and Molecular

Let me explain all three separately:
1. Molecular Biology – what is called molecular biology. In which cells, various organelles, DNA, RNA, proteins come to mind. Simply put, this branch of science deals with the biological interactions of cells with various biological molecules, including the interactions of DNA, RNA, and proteins, and their biological analysis and interactions. Cloning is the most important and fundamental technique of this branch. Using PCR and restriction enzyme, DNA coding for desired protein is cloned in plasmid expression vector.

2. Microbiology – which is called sub-biology. Here, working with viruses, fungi, bacteria, protozoa, archaea comes to mind. Some of the beautiful topics of microbiology are ‘genetics and evolution’.
Some micro-organisms (germs) and other animals can cause various infectious diseases of birds, so all these diseases, as well as their prevention and treatment and discussion and research on diseases of our body are hot topics in microbiological science.

3.Biochemistry – It is a bridge between biology and chemistry. Chemistry explains how all the functions of the body are related to life. Different components of cells, such as carbohydrates, fats, lipids, nucleic acids and other organic molecules, genetic code (DNA, RNA), protein synthesis, signal exchange between different cells. etc. are the topics discussed in this branch.