I've learned some common phrases, and I can't understand what is the diffrence between ca va, comment ca va, and ca va bien. Can you please help me?
I will try to explain all that.
The normal way to ask someone if they are doing well is: 'Comment vas-tu/allez-vous ?' ('How are you going/doing?). And the normal answer (if you are doing well or if you do not feel like talking about your problems) is: 'Je vais bien. Et toi/vous ?' ('I am going/doing well. What about you?')
This is rather direct and personal, though. To make it less personal, we ask: 'Comment ça va ?' ('How does it go?/How are things going?') or even only 'Ça va?' ('It goes?'). And the normal answer is: 'Ça va bien' ('It goes well/Things are going well'). But this is still too personal for most people, because it seems to mean 'I am doing well.' So we use the low-key version: 'Ça va' ('It goes'), which means: 'Normal, just another day, nothing special' or in some cases: 'I have tons of problems but I am not willing to talk about them.' It will depend on the tone, actually. A very sincere 'Ça va' with a big smile will mean that you are doing great.
Ca va bien is 'i'm fine' or 'i'm okay' or i'm feeling well. You can know this by the 'bien' at the end. Ca va is a bit the same, but is rather 'i'm well' or something without the 'bien'. Comment ca va is a question. Comment means 'how', so the phrase is just 'how is it going?' or 'how are you?'.