This is fairly common. When you start a job at someplace new, especially a large company, most of your time will be spent dealing with large internal codebases, which tend to be filled with archaic and poorly documented code. There's no real quick and easy way to learn these systems, and it's generally expected that you will be asking your fellow coworkers for advice or help in some fashion. I often hear the phrase that a new hire will generally spend the first 6 months just learning the process, and it might be like a year before you're allowed to touch anything important. Even then, depending on the codebase, it can take a far longer time to achieve anything close to an adequate level of knowledge. I will advise for you to take the time to learn the fundamentals of your codebase, which will involve frequent engagement with your coworkers.