This is definitely doable w/ just a single Grid block.
Do these steps:
1.) Insert 1 grid block.
2.) Place 5 columns in it.
3.) Add 15% padding to all of the columns.
4.) For the first 2 blocks, set 50% width.
5.) For the last 3 blocks, set 33% width.
6.) For the horizontal borders: set Top and Border size for each of the column containers.
7.) For the vertical/separator borders on First Row: Set left border for the 2nd column of the first row.
8.) For the vertical/separator border on the Second Row: Set the left and right border for the 2nd column of the second row.
9.) To make the grid full width: Make a Layout Element, set the content container to “Full width(no padding).
You’d arrive at something like this.
https://share.getcloudapp.com/6quPoR40