There are contractions:
Have/has. I've (I have), he's (he has), they've, she's
Is/are/am: I'm (I am), you're (you are), he's (he is), they're, she's, it's
Will: I'll (I will - common in writing), she'll (she will - hardly ever used in writing), he'll, we'll, it'll
Not: don't (do not) can't (can not), won't (will not)
You just have to practice them. You don't need to write them, but you do need to hear them. In writing they will always have an apostrophe (').
"Wanna" and "gonna" are not words. They are used in dialog in literature to represent uneducated speech. Don't use them yourself.
"Its" and "it's" are two different words. Many native speakers confuse them when writing. The possessive adjective "its" as in "the car is in its garage" means the garage belongs to the car. The contraction "it's" means "it is".