How can I turn into a good developer C#

Three things: Read, Do and Learn.

You need to be passionate at what you are doing to become good at something. Learning C# is easy but it's hard to master it. That's why we are still here to code, code and code to gain experience and learn about our mistakes. Bottom line is experience matters to be good at something and accepting our mistakes makes us better.

Here are few tips:

Read books, tutorials about C# and OOPs
Start at the basics and understand how stuff works (concepts and methodologies. patterns and practices)
Practice- code, code and code and apply the new features you've learned
Apply what you've learned in real world scenarios
Gain more experience about the technology
Love your job and be passionate about it
Be open minded and listen to ideas
Give back to the community by participating through forums or writing articles