Everything has a beginning except for God, and a reason why it began. People have theories, and different stories but what is the real reason?
You are assuming a lot of things that are not true. For instance, God did not create animals, He commanded the waters to produce them. Genesis chapter 1 records just three occasions when God created: verses 1, 21, and 27.
A human trying to understand God is like a Ford trying to understand Henry.
Revelation 4:11 says: It is because of God's will that all things " existed and were created."
From the beginning, it was Jehovah's will for earth to be filled with perfect children of Adam and Eve. Jehovah loves people, and it is his will that obedient humans live the way he intended.
Love played a key role in Jehovah's creative work. It wasn't that he was lonely or need companionship, he's complete and self contained, lacking nothing that someone else might supply. His love, an active quality, naturally moved him to want to share the joy of life with intelligent creatures who could appreciate his gift of life.