weird spacing post grid front page

So I am currently working on creating my own website for the first time ever. It will be a blog+. I am a total newbee to this but have come suprisingly far so far!

Right now I am having trouble with something. I hope someone could help me out with this! Preferably in easy language hehe ?? Some CSS code would be great!

My issue/wish:

I have a static page as my front page, so I can have my blog posts on my blog page. But I do want to show 3 or 4 blog posts (the most recent ones) on my main page, sort of as an invitation and sneek peak. To achieve this I have the plugin ‘the post grid’ installed. Before that I had ‘post grid’, but both of them are doing some weird things, but I feel like it’s not the plugin but something within the sydney theme (or somewhere else?). All the videos etc. I watched about the plugin don’t show this problem.
I have the 4 most recent blog posts from left to right now on my front page, like I wanted. But they only take up the first 2/3 of the space (from left to right), and leave the last third blanc. Nothing I do seems to fix this. I just want the 4 columns in the middle, and to take up as much space as possible so they’d become a bit bigger. Now they all are really pressed together and narrow. It seems as if there is something within the last third to block the grid from going there as well? (note: I do not have a sidebar anywhere on my site)
I don’t know what’s going oooooon.

Or would there be an easier option to achieve 4 recent posts on front page?

Thanks in advance!