Is there a way to change the yellow font in for example Minecraft to black?

For example, here at Enzeilspieler, I would like to have it in black and not this yellow when I go over it with my mouse?

This is possible with Texture Packs

But how can I change that file?

I do not know the textures like that. Just open the Texture Pack with 7-zip or the endless 40-day trial version of WinRAR. If you can speak a little English, you should be able to find it quickly