Hey Sahil_Firoz_090, thanks for getting in touch!
I'm sorry that the game keeps freezing. This is not a very common issue. Please try verifying the games files:
1. Restart your computer and launch Steam
2. From the Library section, right-click on the game and select Properties from the menu.
3. Select the Local files tab and click the Verify integrity of game files... button.
4. Steam will verify the game's files - this process may take several minutes.
Also, please try temporarily disabling background applications:
1. Close all open programs and reboot your PC.
2. Press the Windows and R keys simultaneously.
3. Type msconfig into the box and press Enter.
4. Choose Selective startup.
5. Uncheck Load startup items.
6. Reboot your system.
Test the game, and let me know if this works.
- Ubisoft Support