I started to learn Finnish a few months ago. There is a great intro-level Finnish course on Duolingo that is quite entertaining and lets you try the taste of Finnish before you'll be ready to make a deep dive into the language. But it provides just exercises and doesn't explain anything, you are supposed to guess what is right just based on provided examples. It mostly works, but sometimes you are left with an open question "why?" without a chance to get an explanation.
The truth is, originally the course had proper lessons with explanations of basic grammar mixed with some jokes about Finnish culture. The lessons were removed in 2022 for some mysterious reason, and just exercises are left since then. Duolingo fans from the duome.eu preserved all these materials on a single page. I didn't like that the page doesn't allow to track progress of learning, so I made my own pirated version with blackjack and bells and whistles.
It's mobile-friendly and can be added to the home screen as an app. You can mark chapters that you already learned, and they will become green. Overall progress is displayed in the Table of Contents on the top of the page. You can quickly scroll to your current chapter by using the "triangle down" button. Each chapter mentions section and unit where you can find related exercises on Duolingo today. Each unit on Duolingo corresponds to a chapter in the guidebook, and they go in the same order, so it's convenient to read the guidebook and do the exercises in parallel. Just bookmark the guidebook page and visit it whenever you move to a next unit on Duolingo to read the next portion of grammar. No more guessing what the green owl wants from you!
Learning any new language is always a long road and it's important to find something that would help you to keep up for a few years. Tracking progress of learning might help with keeping motivated. Sometimes you might not feel your progress (that is quite subjective and can be discouraging), but tracking your daily progress does the trick and makes it visible so you can actually see it. This is why I also track how much time I spent on learning Finnish. Each lesson makes me closer to my target of 1600 hours.
Keep in mind that Duolingo alone is not enough. It's a great intro into the language, but you'll eventually need to take quite a few more courses if your goal is actually to start speaking. The Duolingo course is just roughly first 100 hours of this journey.