My first is a latin-based language, and I know just the latin script, I have no experience writing in cyrilic script, greek script, and hebrew script. Is it possible to learn Hebrew or Greek from books and internet without taking a course and without a teacher?
I learned the Hebrew alphabet in 2017 from books and an app that would prompt me to write a certain letter and grade me on my handwriting. I started learning the actual language the next month and was writing full sentences shortly after that. I am now having conversations in Modern Hebrew with native speakers, having never taken a live, instructor-led course.
Self-learning an alphabet is possible, and not that hard either. I probably spent no more than 1-2 hours a day learning the alphabet for about two or three weeks.
Now, I would strongly recommend that you not tackle three writing systems at once! Identify the language you want to learn and then learn its script. If you want to learn Russian, go learn the Cyrillic alphabet and the language! If you are looking for Greek, you know what to do. If you want to learn Thai, stop reading this answer and go get a book or an app!