IMHO I think it is the best framework to build software on. Since you are coming from Java, It should not be too difficult to adjust to C#. NET Core has come a long way. NET6 is just amazing. With the minimal API, https://docs.microsoft.com/en-us/aspnet/core/fundamentals/minimal-apis?view=aspnetcore-6.0 REST API should be very easy work for starters. When you settle in, you can go more advanced.

Although this is dated - https://download.microsoft.com/download/D/E/E/DEE91FC0-7AA9-4F6E-9FFA-8658AA0FA080/CSharp%20for%20Java%20Developers%20-%20Cheat%20Sheet.pdf it provides you side by side comparison of syntax. Another cool read is - https://betterprogramming.pub/java-to-c-c-to-java-f766c9f659c4

Feel free to reach out if you need any assistance.

Welcome aboard