Aurora77- some of the posters are giving you quite complicated suggestions. The best suggestion is contact an Orthodox rabbi. If you determine you are halachically (according to Jewish law) Jewish through a valid maternal line, you will have the same learning curve in Jewish practice as you would if you are a gentile and required to (and decide to) convert. You will have the same learning curve, in fact, as many of us who grew up non-Observant and came to Torah Judaism as an adult, so called baalei tshuvah (BTs).
You need some good basic reading material. Two books I found helpful when I was becoming frum (Yiddish for Observant) were “To Be a Jew” by Rabbi Hayim H. Donin and “How to Run a Traditional Jewish Household” by Blu Greenberg.
Don’t get hung up on the nitty gritty of the law and do as my Rabbi counseled: take on ONE thing at a time, ONE thing that you can commit to changing.
And of course, the best teacher is a living human from whom you can learn the subtleties of Jewish living. It’s not all “do this and don’t do that” kinds of prescriptions and prohibitions. There’s a way of talking and interacting in the world that, unless you experience it, you won’t even realize it’s a choice and way of living. There are really people who speak and carry themselves consciously in a genteel manner, according to Torah values.
For example, in speech, a frum person might describe someone as a “not nice” person instead of “bad,” framing things in a positive manner. Or constructive criticism with a gentle edge: I was wearing a wrap-around skirt and my rebbitzen commented that a different style would be more becoming – rather than tell me my skirt was not appropriate. To a child doing something wrong: Es passt nisht (Yiddish – that behavior doesn’t become you; meaning “you are better than that.”) You can’t get this from books.
Learning the laws is the smaller part of the change/conversion. It is learning to THINK like a Jew that will be your life’s endeavor, leading to ACT like a Jew according to Torah. There’s a whole area of learning devoted to mussar – character development. But slowly, slowly. Take baby steps so you won’t be overwhelmed and be daunted by the amount of effort it will take. After 20 years you’ll look back and wonder how you lived any other way.