When do you use "ser" and when do you use "estar"?
Ser- a factual quality of something of someone that doesn't change (for ex: where one comes from) Estar- is for a state of mind or of being (for ex: to be sick)
How do you know when to use the verb "savoir" or "connaître"?
Both mean "to know", but "savoir" is use when you know how to do something or where or who or what something is, while "connaître" is to know someone or something well/on a personal level.
When do you use "then" and when do you use "than"?
"Then" expresses a moment in time, while "than" implies a comparison between two things.