And here's the super smart guy :-p (just kidding, I'm actually not that smart.)
When two words are synonyms then the difference between them is context depending. So, in some cases they are the same and in other not.
"Manche Menschen mögen Katzen" = "Einige Menschen mögen Katzen"
(The meaning is abstract: "People who like cats exist")
"Manche Menschen gehen die Straße entlang" ≠ "Einige Menschen gehen die Straße entlang"
(first sentence, the meaning is abstract: "People who walk down the street exist." I maybe can't see them right now, but their existence makes sense.)
(second sentence, the meaning is concret: "A few (a group of) people walk down the street." I can see them and point with my finger at them. There they are!)
Even that beeing said. I recommend that you follow Felix advice and don't worry about it too much. For your most interaction it's probably not making any difference. When you get a lot of input via books, movies and conversations. You will use them correctly eventually anyways.