I’m ensuring my website is responsive across different screen sizes. It all works fine on Mobile size apart from Kindle Fire 7 / Galaxy S5 size. Whatever changes I make, buttons appear right at the very edge of the screen. It’s unaffected by padding, making my Flexbox vertical, using a grid, changing the positioning etc.
The problem is that Samsung Galaxy S5 is quite an old phone and the app isn’t optimized well for that phone. The app is very glitchy and it has a lot of problems even on new phones. I would recommend you to buy Kindle Fire starting with the second generation of Kindle Oasis. I have my Kindle for 2 years and I am very pleased that I bought it. It saved the space in my house and also it saved my time. Before I got my Kindle I was ordering books online, and I was always waiting some days before the book was delivered. Now I just download them right on my Kindle. If you are interested just watch some kindle oasis review.