STM32L4 clock set up
I have to agree with other comments already provided, simply use CubeMX to generate proper clocks. It is built into CubeIDE which you can use to develop code and debug it.
So with CubeMX, set RCC to use HSE with crystal, then in the clock configurarion, set external crystal to be 4 MHz, select HSE as PLL source, and select PLLCLK as system clock. Adjust PLL input divider M to 1 and multiplier N to 60 and postdivider R to 2.
Yes the system tick timer (generally) runs as sysclk/8, but that is just a timer, the CPU clock is still 120 MHz.