so if there is no operating system for 8bit microcontroller so is there any chances to do the project in Atmelstudio with out operating system
Yes, there is. You might want to use the Arduino IDE instead of Atmelstudio because there is much more software available for Arduino and especially if your new to Microcontrollers the Arduino IDE will be easier to handle. But it's just a matter of personal preferences, so you can use whatever you want.
If you're new to microcontrollers, start with easier tasks than using a CAN bus, to get familiar with the development tools and the hardware interfaces. Once you have some experience move to the more complex opportunities.
but when i searching for operating system for arduino i found like Duinos ,FreeRtos
It depends on how you define an operating system if these projects are really operating systems or just development frameworks. In my eyes they are the later your opinion may vary.