How to revert to default UI settings in iPhone SE?

iPhone SE, 64GB

iOS 12

I have just updated to iOS 12 and was going through changes in settings app. When I adjusted to larger size in text size under the Display and Brightness. It successfully changed the dynamic texts, but i didn’t like it as it was not impressive on my iPhone SE.

So, I decided to rollback to original font size and I did it and tuned to smaller fonts in the same way I increased it. But it couldn’t successfully transform to original. List view of settings app is still expanded and there is some unimpressive line spacing in texts of iMessage. Boxes are larger. Though fonts size has decreased but it didn’t decrease the text box and added certain spacing or margin. For clear understanding, I am attaching some screenshots.

Please, help me out in this. I want the old UI as liked it most.