Hi Halil,
Thanks for using Syncfusion products.
As we have analyzed, these warnings are shown when the build type is set as Build + IntelliSense and you can still run the sample browser without any issues. However, you can clear these warnings by setting the Build type as "Build Only".
If you are still facing any other issues, we kindly request you to provide the error log for helping you further.
Please check and get back to us if you need any assistance.
Regards,
Parthiban S