Hello Asamichan, 不能 means can not ,must not ,should not 不会 not able , not having learned to do something It means also improbable or unlikely. 不得 may not ,must not , may not be allowed 不可能 impossible, cannot, not able

不能:can not not allowed. 不会 :have no ability to do sth 不得: have to do ,have no choice but to do sth 不可能:impossible

不能不会不得 indicate mustn't but 不可能 means not possible or shouldn't

不能：means cant`t. eg1:You are right, I can’t change the past and run from it.I should learn from it. eg2 :i`m sorry i can`t. 不会：generally incompetent or you have no ability to do something.for example:They are not capable of doing the work. or He is unequal to dealing with the problem. 不得：means mustn`t or prohibition. eg:no smoking!不得吸烟。 Forbid to go sight-seeing.不得观赏。 不可能：means:impossible,Perhaps not. eg1:this is impossible. eg2:it can`t be . eg3:A:If the sun were to disappear, what would the earth be like? B:you think too much,it can`t be happen. in a word:in chinese says, sometimes they can transform each other,but the means can not be change.for example:我不会做这件事情。我不能做这件事情。it also means "i can`t do it." ok.good luck~