Fun to see GM Axel Smith mentioned, I used to be his student as a teenager, when he was still an IM. Great teacher and just a wonderful person overall. I can vouch for his methods, even if I was a teenager when I practiced them.
This is a great article on how to improve chess as a beginner, from the perspective of a former beginner. Basic recognition of patterns is the bedrock of tactical calculation. And focusing on problems that can be solved quickly is a good strategy for building it.
I do want to champion the cause of harder problems though, because there is more to calculation than pattern recognition. And this will become more and more important above the very impressive 1500 the author managed to reach.
Calculation is a conscious mental process that needs training in its own right. It involves the ability to visualise board states, remember where you are in the game tree, enumerate candidate/forcing moves and threats, heuristics like the method of elimination. None of these can be trained purely through these simpler problems, only through slowly taking your time applying all these techniques. This is why blitz rarely leads to an improvement in your base ability. The only way to build out your ability beyond what you can immediately recognise is to really struggle with positions you can't solve in 8 seconds, or even 8 minutes. This happens naturally if you play longer time controls(and actually spend your time). It's also tremendously helpful to join your local chess club and work through some problems with a stronger player to guide you. That's also a lot more fun to most people.
Learning chess doesn't have to be just a lot of rote exercise. You can also read books on positional chess, pawn structures, endgames, and openings. No, they don't decide games as much as tactical mistakes but they certainly influence games profoundly whether the players are aware of them or not. And a more "holistic" approach can be more motivating.