The CPU frequency is stuck at 0.78GHz and under full load (while running Prime 95) the CPU usage doesn't go above 34%.
I have tried to reinstall the system (windows 10) with all power setting set to performance and I have update the BIOS but it didn't solve the issue.
You need to check the BIOS configuration. It sounds like you have a limitation being imposed by something there (max clock, max power, etc.)...