please help change css for jannah

hello
i want change archive layout for jannah for grid

I want it to be displayed as a grid in the WordPress post archive section with only 3 columns
Only post photos and post titles
This show is on tablet and computer
I want it to have a white border according to the submitted form
In mobile mode, I want only WordPress posts to be displayed as 1 column
As before, only have a photo and post title
With a white border

Thanks for helping me make the archive look like this
None of the templates have this particular shape

Please tell me what styles I need to add or what file I need to change

For convenience, I sent my favorite photo, but these photos belong to another format
But I want the final shape to be exactly like these photos
Thanks for your tips