It's possible to turn wifi frequency at 5.8 instead 2.4 Ghz?

Yes. Switch to manual and select a channel from 149 up. Channel 1 to 11 are 2.4Ghz and channel 149 up are 5.8Ghz.
Higher frequency gives you lower range.

The drone should switch to 5.8Ghz by itself when 2.8Ghz channels are too busy.

Manually if not automatically selected, but the signal strength is not as capable as the 2.4 GHz which unfortunately is far busier.

Hello and good day Renato61. Thank you for reaching out and for the inquiry. For the CE version of the DJI Mavic Mini. Users can switch the channel to switch between 2.4 GHz and 5.8 GHz. First, set the channel mode to " Manual ", and then before the aircraft takes off, users can choose from the channels shown on the bottom of the application. A channel numbered above 140 is a 5.8 GHz channel, and there are five of them ( four in Korea ). The other 13 channels are 2.4 GHz channels. Kindly please observe local laws and regulations. Thank you.

Thanks, I'm trying to have a greater reach. Today on the beach already over 400 meters and without obstacles at 2.4 it gave me a weak signal

Renato61 Posted at 2-15 10:29
Thanks, I'm trying to have a greater reach. Today on the beach already over 400 meters and without obstacles at 2.4 it gave me a weak signal

You are very much welcome Renato61. If you have any other inquiries or concerns with DJI or with your DJI Mavic Mini. Please feel free to post it here at DJI Forum. We are here to help and support you. Please stay safe always and keep on flying.

Renato61 Posted at 2-15 10:29
Thanks, I'm trying to have a greater reach. Today on the beach already over 400 meters and without obstacles at 2.4 it gave me a weak signal

5.8GHz, as mentioned, should give you lower range. Which is not what you want.

Denny-R Posted at 2-15 10:43
5.8GHz, as mentioned, should give you lower range. Which is not what you want.

I believed the opposite, the most expensive drones if I am not mistaken do not use 2.4 ghz

Mine only shows 5.8Ghz and if I out on manual do not get channels lower the 140, is it CE or FCC

Suren Posted at 2-15 11:53
Mine only shows 5.8Ghz and if I out on manual do not get channels lower the 140, is it CE or FCC

You have FCC version. It is not so bad...

Suren Posted at 2-15 11:53
Mine only shows 5.8Ghz and if I out on manual do not get channels lower the 140, is it CE or FCC

5.8GHz only is the FCC version I think. It has therefore full transmission power. CE versions have a power limiting IC installed.

Renato61 Posted at 2-15 11:39
I believed the opposite, the most expensive drones if I am not mistaken do not use 2.4 ghz

Lower frequencies travel further, so 2.4 is theoretically better for range. It is however a very busy frequency so sometimes you need to switch to 5.8 (which has a max range of 500m for the CE version). The FCC version has just 5.8 but it uses a lot more power (25x according to some measurements) for a max range of 4km.