Unfortunately, you cannot doengrade your iOS. We have many great members here, and someone will come along soon enough to help resolve your issue. In the meantime: Hello, and welcome to the forum!
The iPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the iPad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.
Encore une fois, nous vous souhaitons la bienvenue et sommes très heureux que vous nous avez rejoint!
Once again we welcome you here and are so pleased you have joined us!
Did you do a reset on your iPad after the upgrade? It is a recommended step after any update.
Hold the power off button and the home button simultaneously, keep holding them in and you will see the power off slide appear and disappear, wait until you see the Apple logo appear before releasing the buttons. It will take a little longer for your iPad to start. Let us know if this makes a difference.