What is next step after ADO.NET and OOP that studying. I need advise because i'm beginner

There is no real order of importance. To code in .Net, you have to understand the framework.

The key isn't learning everything - the key is learning everything you need to learn, as soon as the requirement presents itself. Pretty soon, you'll know a lot about everything. In the biz, we call that "experience", and unfortunately, it takes years to gain.

As an example, back in 2009, our company decided they wanted to re-factor their flagship app from Oracle forms to .Net, I argued against going with WPF (because WPF served no purpose in terms of app functionality), but they decided to do it. That was in the frist week of January. The project was slated to being on March 01, so I spent the next two months on my own time at home, learning as much as I could about WPF (I had never used it prior to that time). In that instance, I was lucky to get a heads-up and was relatively ready for the project by the time it began.