No worries about the review of the PR. As stated in the GitHub repo, your PR doesn't need to be merged — that can take time and we don't rush that process.
When we'll go through the submissions for a project, we'll take a look at your proposal and PR and will review them to rank everybody applying for the same project.
So you just need to focus on writing a good proposal and PR. Start with something small and react to feedback. If that one worked well, you can continue with another one if you want. One good, small PR is better than opening multiple half baked ones or tackling a big problem and getting stuck.
Hope that makes it clear