Nespi 4 case fan speed control - HELP

Hello, noob here
I need help to control the fan speed in my Nespi 4. I have put a 5v mini fan in and connected it up to the dedicated power pins. My problem is that the fan sounds like a jet engine as its going full speed and I need to figure a way to control the speed I have found lots of yaml scripts to control a fan but nothing seems to be working. Im rather new to HA (loving it) and just need some guidance on what I should do or not do.

Many thanks