Caveat, I don't actually speak the language, but I do speak several languages, including one non-European language that has been a challenge. Also, my son has been taking lessons twice a week since the start of the pandemic, and has his classes 100% in Japanese these days, and I've watched his progress.

I would first start with a couple of apps and put in an hour or so a day for several weeks. Start to learn the basics of kanji, and get a firm grasp of the general structure of the language. When you've done that, start regular iTalki or Preply classes, and stick with it. Don't think of it in terms of arriving at a destination, since you'll never quite be satisfied, but as a process, something that becomes a part of your identity. Motivation, thinking long term, and enjoying the process rather than being impatient about the results are the key.

You may already know all this, especially if you've gone through the process of learning a challenging language like Icelandic as an adult already, but I think it's generally helpful advice for any language study.