What do you mean by "normal verbs"?? ;) "Make out" is one of those phrasal verbs that has multiple meanings, but the good news is that the specific meaning is clear from the context. For the example of "see", it actually means being able to see something which is obscured or distant (eg. "I made out a house in the fog" - you'll have both the object and also the thing that makes the object difficult to see in the sentence.) For "understand", the idea is the same as "see", but figurative. Really, just get used to using phrasal verbs. They crop up all the time - you can't avoid them (plus, it sounds weird if you try to). "Go off" has other meanings aside from explode. "The alarm will go off if you trip this switch." "The festivities went off without a hitch." You'd use "blow up" fairly commonly, but "explode" is almost as common.

These are called phrasal verbs, which are the combination of a verb and a preposition. They have completely different meanings from their usual verb/preposition meaning (e.g., if we "look up something in the dictionary," we don't actually lift our heads and look up to the sky! In this case, "look up" means to research something). So yes, "make out" means to be able to see or understand something clearly. Examples: "I can't make out who is coming down the street—she's too far away." "He has a strong accent, but I can still make out what he's saying." In fact, "make out" has several meanings as a phrasal verb (it can also mean a result, or deep kissing). "Blow up" is a common phrasal verb for "explode/bomb" but can also be used in a more literal way when you blow up a balloon or a rubber raft. You just need to learn phrasal verbs just like you learn other vocabulary words, because all native speakers use them all the time.