UX | Button Design and Basics

I am currently starting doing Webdesign and UX and I am new to this topic. I have a webpage where I have various buttons. Positive Actions are Green and negative actions are red. An Edit-Button is blue.

The problem is, all of the buttons have these pattern. That means even a Button, which adds something to a list, is green and the one who deletes this is red.

For me this is bad, because all buttons look the same, even if some have a bigger meaning, like submitting something.

Do you know how to solve this, or what techniques are there?

And also being new to all of this, what do you recommend to read or watch, to get to know how to design a website and maybe to create a styleguide.

Thanks.