How to get altitude data from GPS and accelerometer

I want to get altitude data.
So I connected GPS to the flight controller. The flight controller has a built-in accelerometer.

GPS data is available, but it looks like the accelerometer isn't being used.
I manually move the drone up and down when I get the data, but it is not reflected in the altitude data. But the accelerometer is reacting.

Is it possible to apply accelerometer data to altitude data?

I use a manba mk3 flight controller.

To get accurate altitude data you need a barometer. Some FCs have barometers built-in, or you can buy an external one and wire it to your FC via I2C if it supports it.

Can you confirm exactly which FC you have? Photos and a CLI dump will be useful.

Agreed. You need a barometer for the most accurate readings. From my experience GPS altitude readings in most cases are useless and too inaccurate / erratic. Once you have a barometer installed you will also want to run the following commands in the CLI to force use of the barometer for altitude readings. Make sure you also put a piece of open cell foam over the barometer chip.

Thank you for the advice.
I will send you an image of the flight controller you are using.
This flight controller has a built-in barometer.

I will try this command.