Help with full width row on mobile

Hi, I tried to design some kind of stick menu with buttons on a single post row, but I can’t make it work full width with buttons with equal sizes.

What I did was:

Row with two sections. Each section with internal rows with 3 sections. So, I put 6 full width buttons. One on each section on internal rows.

But it doesn’t work on all mobile sizes full screen. It gives me a blank space on one size in bigger phones, and if I try to enhace the size of the buttons, it’s bad for smaller screens.

Here’s one solution I found, but it looks terrible: https://www.topensandoemviajar.com/agenda-cultural-sp

I want to make all the buttons same size, so they occupy all the row (without paddings) in all sizes of mobile.

(Please delete the link after seeing this).

Thanks.