I wanna insert the accelerometer and gyroscope in my solution. Now, I am using the nRF52840 and I wanna know if you can recomend any library and/or shield to add this one in my board.
You could use the MPU9255, which includes both a gyroscope and an accelerometer.
Down below is a link with drivers, libraries and examples for communicating with MPU9255 (and other devices), and works with SDK14 and nRF52840.
Examples for nRF52 series and MPUxxxx
Best regards Simon Iversen.