There are only a few basic softwares for graphic design, many online tutorials and many tutorials in bookstores. If you have the ability to teach yourself, you can easily learn several softwares. If you don't know how to teach yourself and can't even use the mouse, it's foolish. I suggest you go to school to learn. Because everyone's foundation is different, some self-study with good foundation becomes.

As you know nothing about graphic design, I think you'd better not plunge into it first. I suggest you find a school to learn. Don't expect to learn graphic design, but you can get in touch emotionally through learning. In fact, training institutions can't teach you graphic design, but at least they can make you better than those who don't know anything. Graphic design is a skill, just like a chef. The school has taught you recipes for cooking, but a real chef won't follow them. So most abilities are self-taught through work.

It's purely advertising, just like the card downstairs. In this industry, you don't read certificates. Mainly depends on your design ability.