How can I contribute more after the wait time. Or how long does it take for the full 25 contributions?

You can contribute once every 20 minutes but if you haven't contributed for a while then there will be up to 25 chances to contribute accumulated. Just hit the donate button 25 times to keep contributing. Once the 25 are used up you have to wait 20 minutes to donate 1 more time etc. Or wait around 8 hours and you will have 25 chances again. You can also donate with diamonds up to 50 times a day.