Thank you for your feedback!
The problem with the mobile website is a bug that we'll look into fixing. As for there being a lack of ways to jump to the series/volume, we'll add that to our list to look at for a future website update.
As for the app, unfortunately we have had a lot of problems over the last year getting the app through the Google/Apple Store review process, so we have diverted our development resources to the website and backend infrastructure instead. We plan to resume working on the app as soon as we can, but our progress is still largely dependent on whether the app stores will play ball or not.