I considered saying the same thing, but C# has been around almost as long as Java at this point, and I believe it’s commonly used for teaching, so I have a hard time believing there’s a shortage of learning resources. Starting with Java seems like a waste of time if your goal is to learn C#, because you can learn the concepts equally well in either language, but if OP starts with Java they’ll end up spending a lot of time unlearning Java quirks and APIs while learning the equivalent stuff for C#.
Getting exposure to the language only once a week will definitely hinder you a lot. When learning a language, there’s a bunch of stuff you’ll memorize without even thinking about it if you spend time working on it every day, but it will be hard to remember if you spend a week between learning sessions.