Albert Einstein developed the theory of special relativity in 1905 and the theory of general relativity in 1915. While he was the originator of these theories, it is important to note that scientific theories are often refined and expanded upon over time by multiple researchers.
Einstein himself continued to work on and refine his theories throughout his life, collaborating with other scientists and considering various aspects and implications of relativity. The theories of relativity are highly complex and have profound implications for our understanding of space, time, and gravity.
It is fair to say that Einstein had a deep understanding of his own theories and made significant contributions to their development. However, like any scientific theory, the full understanding and implications of relativity are a collective endeavor that involves the contributions of numerous scientists over time.
It is worth noting that scientific understanding is an ongoing process, and theories are subject to refinement and revision as new evidence and insights emerge. This applies to Einstein's theories of relativity as well. While Einstein made groundbreaking contributions, our understanding of relativity has continued to advance through the work of subsequent researchers.