Next and previous-buttons showing post title

So, my blogposts previous and next-buttons are displaying the blog posts titles. This appears pretty chaotic when displayed on a smartphone as the buttons is weirdly overlapping each other. I want to change the text to “Next” and “Previous” on the buttons instead.

Here’s a screenshot illustrating the problem:
https://farm3.staticflickr.com/2946/15177072597_d526b74578_o.jpg

First of all, yes, I’ve already read the https://codex.www.ads-software.com/Next_and_Previous_Links
and as a confused rookie I don’t understand anything of it (I have not been working with much php before, but I do want to learn it.)

I’ve searched for hours on this topic in the forums but I simply can’t get it to work. What php-file am I supposed to look for in the first place? Functions.php? single.php?

And what code needs to be changed or added?

I am using a child theme of the theme Minamaze.
Please help a total noob in despair.