Fortigate Wireless Speed Problem

Discussion forums are only supported in English. 
From the translation, I understand you are getting a slow speed (80Mbps) when connected to an access point. 
1. What is your Fortigate model and Firmware version

2. What is the firmware version on FortiAp 231F

3. Are you using tunnel mode or bridge mode ssid

4. How much speed you are getting on your LAN network

5. Perform a multistream Iperf test on the fortigate and on the port where the access point is connected via the switch.

6.Check the latency and packet drops

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Use-cases-for-the-diagnose-traffictest-command/ta-p/197784

You can use the iperf servers from here:https://speed.fortisase.com/

"So I’ve been digging through spec sheets and IEEE standards for a minute here… Looking specifically at your FortiAP model, the FortiAP 321E, it’s rated for around 450 Mbps for the 2.4ghz radio and allegedly up to 1,300 Mbps for the 5ghz radio, but speaking with our wireless specialist achieving these speeds generally is not expected. To get 1,300 Mbps requires larger bands for 5GHz channels in full duplex which in an environment with a lot of clients could cause more network congestion. Around that 860 Mbps is about what is expected at the limit of the technology we have at the high school https://tutuapp.uno/ .

If you are facing any issues with your Fortiap device's throughput, it is impossible to provide you with a solution without looking at the technical details of the traffic. So ATM my recommendation is to open a ticket with your FortiAP serial number.