Hey AllexRo,
What RouterOS software version are you running? The only country options for mine are "canada2" and "united states3" and no DFS frequencies are listed. Is there a setting to enable using DFS channels?
Here are the allowed-channels on wlan3 when I have the channel width set to 20mhz:
[admin@MikroTik] > /interface wireless info allowed-channels wlan3
channels: 5745/20/ac(26dBm),5750/20/ac(26dBm),5755/20/ac(26dBm),5760/20/ac(26dBm),5765/20/ac(26dBm),5770/20/ac(26dBm),5775/20/ac(26dBm),
5780/20/ac(26dBm),5785/20/ac(26dBm),5790/20/ac(26dBm),5795/20/ac(26dBm),5800/20/ac(26dBm),5805/20/ac(26dBm),5810/20/ac(26dBm),
5815/20/ac(26dBm),5820/20/ac(26dBm),5825/20/ac(26dBm)