Well, if you have zero knowledge of Photoshop, that’s probably a good place to start. The author answered his own question. I can only add that at the moment designers use two main programs for designing websites and mobile applications. They are Adobe Photoshop and Sketch App (for MacOS). There are, of course, others, but it’s better to start with these.
But whether it is worth starting to do web design, it’s up to you to decide. It should be your choice. And if you want, why not try.
A little clarification. Even if you have MacOS and you decide to work in Sketch App, you still need to know how to use Photoshop. Because very often, designers have to edit images for the site, do retouching photos for the layout and more. Sketch can’t handle that, it’s just not designed for that.
Start by learning how to use Photoshop. Learn how to use basic tools. It is desirable to apply hotkeys in your work. This will help you save time in the future.
In the process of studying, try to create something small. For example, banners, design for groups in social networks. After all, this is also a web design. When you get it, then you can move on to larger projects. Move towards the creation of business card sites, and so on…
Naturally, in parallel, you should study related subjects. These are modular grids, typography, color theory, layout, usability, SEO, etc…
Unfortunately, I do not really understand how you can design a multipage site without knowing how the site is technically structured from the inside. It is not enough just to “draw” a nice menu, pick up pictures, add frames and insert texts. You have to understand whether it is possible to implement, how it will work, what and where will be displayed, how the user will interact with the Web site …

If your desire to create web design is great, then learning the basics of html and CSS should not be a problem. That’s why if you plan to be a website designer, then at least a minimum knowledge of layout is a must. You can start to learn them not in the first place. But how sites are structured, what their structure is, how texts and headlines affect the promotion … It is necessary to know.
To be more interesting to understand, start with creating your own site. So kill two birds with one stone – and the first design this site will try to create a platform for the future portfolio will get.
Hobby is certainly good, but web design is more a profession than a hobby. What is the point of creating a site in the form of a picture, if you do not plan the layout and further use?
And on the other hand, if you create a site for the customer, you must understand what function the site should perform and how this can be achieved through design. You really have to understand it, not just draw a beautiful site.
Although, of course, in the low-price segment, there are often customers who do not fully understand why they need a website. But they immediately give you an idea of how the site should look like in their opinion.
But in the medium and high price segment, often the opposite. Turning, people do not always know how the site should look like, but they know exactly what they need the site, they know the structure and name your target audience. And then, relying on this data, it is you who solve the problem with web design.
I can tell you from my own experience – the lower the price, the more problematic customers. Fortunately, I have long passed this stage, as I wish you 🙂
And the customer is more likely to go to a professional, not someone who has drawn sites – a hobby. Web design is not about beauty – it’s about efficiency. The site must work and perform its functions. For different sites they are different. Read more about this I’ll write another time …

Of course, if you are attracted to art, you know how to distinguish good design from bad, it is very likely to join the profession. But how do you know if you will be to your liking, if you have not yet tried? Drop everything and start learning Adobe Photoshop right away! And time will tell.