Difference between CAN and COULD - Basic English Grammar

In this video, Alisha answers 5 questions. - Does "could" mean ability In the present or possibility? What does "likely to happen" mean in English? - I'd like to know about some American dictionaries. Which one do you recommend? - Can we use wanna, gonna & gotta in formal English writing or speaking? - I have two questions, first is there a difference between “a bit” and “a little bit”, second does one never pronounce the “t” at the end of a noun if we add an “s” after the “t” in a plural form, for example “event / events”? - How correct the expression "and this weather has been happened" in the sense that sometimes the weather was bad in the past.