Hello, @Kazi Sabit,
I have added the code in the mobile Custom CSS section under Theme Settings and it worked: https://postimg.cc/Q9kgfmSB
Here is the proof video of my mobile phone: https://streamable.com/8lw0vc
And the code is not affecting the desktop version as well, It is showing 6 columns, here is the Proof screenshot: https://postimg.cc/TpmdFsgH
Regards 8Themes Team.