1) This vs that.
2) 'That isn't a good bread.' is obviously not the same as 'That bread isn't good.' The adjective behaves differently in those two sentences. Google attributive vs predicate adjectives.
explain it in terms of Czech grammar and then the English translation will be more understandable. thanks
I'm not sure exactly what you're asking for but for anyone to whom this may be helpful... To není dobrý chléb is literally "That is not good bread," while "That bread is not good" would be Ten chléb není dobrý, just as it is in English. The course, as explained above and in comments for similar sentences, distinguishes between the two.
Yes, both 'chléb' and 'chleba' mean 'bread.' Pay attention to the accents, there is no 'čárka' in 'chleba.'
'Chléb' is more formal, 'chleba' more informal.