What are the most effective ways for a beginner to learn a foreign language? Should I enroll in classes or can I effectively learn it online?

i would say we should enroll in class, with experienced teachers

THE MOST EFFECTIVE WAY TO LEARN TO SPEAK ANY LANGUAGE IS BY HEARINING IT THEN REAPETING WHAT YOU HEARD TILL IT GETS SAID EXACTLY LIKE IT WAS HEARD ....SO THE CORRECT TEACHER IS EVERYTHING REALLY...IT COULD BE A PROFFESSER OR A MOVIE STAR OR TV ,OR MOST EFFECTIVLY AUDIO LISTENING OVER AND OVER TO WHAT IS NEEDED TO BE STORED IN THE BRAIN, WE LEARN TO SPEAK BY LISTENING FIRST ....WRITING AND READING ON THE OTHER HAND HAS TO BE TAUGHT BY PREFREBLY A PROFFESSIONAL TEACHER .

no need to take classes or take make online to learn faster u can experience it on the floor with foreign co- emplyee one by one by using notebook and write  to know the meaning of they language

both will be affective enroll classes and online if you want it faster