Overclock

Open Terminal and run the following commands to update the system:

sudo apt-get update
sudo apt-get upgrade

Reboot the system.

Read the actual speed:

vcgencmd measure_clock arm (one time reading)
or
watch -n 1 vcgencmd measure_clock arm (monitoring)

Open the file /boot/configt.txt

sudo nano /boot/config.txt

and look for

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

change to

#uncomment to overclock the arm. 700 MHz is the default.
over_voltage=2
arm_freq=1750

Reboot

sudo reboot

Read the speed

vcgencmd measure_clock arm (one time reading)
or
watch -n 1 vcgencmd measure_clock arm (monitoring)

Full article at

https://magpi.raspberrypi.org/articles/how-to-overclock-raspberry-pi-4