can we use can instead of could what is the difference between these two?

No..

Yeah, could is used to express politeness. You can use can except could but it defends upon the person who you're talking to...

No

The modal verbs can and could represent the ability of a person or thing in doing something. However, there is a difference in their usage, as 'can' is used in present situation, whereas we can use 'could' for talking about a past ability. Both are followed by a base form of the verb.