The more English you know, the more often you use a dictionary. That is to say, an ordinary "English dictionary," one language. One of the important jobs of a dictionary is to give the clearest possible definitions of words that have slightly different meanings. As a learner, what you will find is that there is often one simple, straightforward everyday word, and then a cluster of words around it that have slightly different feelings or shades of meaning. So if you are starting to get interested in understanding differences in meaning between synonyms, I seriously recommend that you start using an English dictionary. The no-cost ones online are OK, and I will say that I am particularly fond of the American Heritage Dictionary--I own a print copy--because I think it has some of the best and clearest definitions. But of course Oxford (Lexico) and Merriam-Webster are fine. Unlike some other languages, there is no official authority for English.
It's often hard to say what the differences are, because they involve cultural associations.
"Massive" carries the two ideas of size and weight. A hot air balloon might be "huge," but probably not "massive."
"Tremendous" often carries the idea of big in a figurative sense, not in linear dimensions. "Newton made a tremendous discovery, one of the biggest discoveries in the history of science." You can't measure the size of the Law of Gravity in meters.
"Immense," "huge," and "giant" all mean something beyond "large." If you say that "the land area of Russia is immense," you mean that it is not just "large."
Literally, a giant is a person--real or mythical--who is extremely tall, while a dwarf is someone who is extremely short. Therefore, "giant" is often used in contexts to describe the largest of a series of similar things, and often to describe human beings. As always, the use might be figurative. Beethoven was a giant among composers. St. Bernards and Newfoundlands are giant dogs. Betelgeuse is a giant star.