Why is the site not displaying correctly on iPhone?

Question

iOS

Good day to all! I have a problem displaying the site rashid.cf on iphone devices. I tried to open it on iphone 5s, iphone SE, iphone 6. In addition, I used not only safari, but also chrome. Everywhere the site looks wrong. Everything is great on desktop and android devices!
Here are screenshots of what the site should look like:

spoiler

And this is how it looks on the iPhone:

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I noticed that the text is not displayed inside the tags <a>and <button>.
I would be very grateful if someone could tell me what it could be!

Answer 1

Thanks to all! Most of the stocks almost corrected.
1) First, included normalize.css
2) Added all necessary prefixes with Autoprefixer
3) Installed MacOS virtual machine on VirtualBox and tried to change different styles in Safari web inspector. As a result, by typing, I found out that the text inside the tags <a>, as well as in some other places, was not displayed due to the FT40 font. I changed the font and the text appeared!