I do suggest you keep the pull requests small, with less than 10 commits each, if possible. And I would also avoid touching a lot of files at the same time, although this is unavoidable some times.
There is no way to speed up review and merging. Maybe if you bribe with millions of dollars one of the people with merge privileges you can expedite this. But otherwise, that's just how it is. Contribute as much as possible. It won't be a waste, you just need to be patient.