I’ve worked a on small project and I made a Roblox style Gui! I have made a post before like this. So heres my Guis
This is what I based it off of
And if you want to take them then heres the link 
https://www.roblox.com/library/9316761697/Roblox-UI
Thanks for checking it out! 
Your UI Is Almost Same Like In The Roblox UI, Nice Job!
It almost looks like the same! Tip: You can get the font and textsize from coregui.
edit:
i replied to the wrong person
Your UI is quite inconsistent; in terms of padding/empty space, alignment, text sizes and text hierarchy.
Your first image just has too much empty space in the middle; you could solve this by wrapping the text across 2-3 lines and centering it to make it full.
Your second image’s title is too big (out of proportion), and not aligned between the top of the frame and breakline under it.
Throughout both images, the body text (“Developers are cools”, “You’re about to shutdown the server…”) should be a lighter font-variant than the title (gotham; sourcesans) to maintain proper text hierarchy.