Disabling Wifi´s powersaving

Edit the next file changing the value from 3 to 2 and after editing reboot

sudo nano /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

[connection]
wifi.powersave = 2

######################################################################

An another way:

If wlan connection disappears every now and then, disable wlan´s powersave.

1. Check your wlan
nmcli dev | grep wlan
2. Add the line to the /etc/rc.local file
sudo nano /etc/rc.local
… add the line
iwconfig wlan0 power off
… if your wlan is wlan0
3. Save and quit
Ctrl o
Ctrl x