Where to start independent study of law?

For a better understanding of the legal system and the organization of the state mechanism, I recommend that you read the textbook entitled "Theory of the State and Law".

After mastering the basic concepts, you can proceed to the direct analysis of the current legislation. I recommend starting with the basics, namely with the Constitution of Ukraine (https://zakon.rada.gov.ua/laws/show/254%D0%BA/96-%D0%B2%D1%80#Text) and Civil Code of Ukraine (https://zakon.rada.gov.ua/laws/show/435-15#Text).