I found a guide on this page and it really works !
I repeat the steps:
1. Go to /system/etc/firmware/wlan/prima/
On developer (beta) roms starting from 6.10.13 version and 188.8.131.52 Global Stable ROM version WCNSS_qcom_cfg.ini file is located in /system/etc/wifi
2. Find WCNSS_qcom_cfg.ini and open this file with text editor app.
Then add this line in the bottom:
3. Save the changes and reboot your device.
What you also can do in this file is to enable WMM:
Search the line WmmIsEnabled = 0
Replace it with WmmIsEnabled = 1