You've done a good job using "those are" in this sentence. You can even see it when you look at the main translation. The mistake you've made was typing the definite article in front of "great words". You'd have to say "To jsou TA velká slova." in Czech for your English sentence to be accepted. :)
"To" is no article but a demonstrative pronoun. Also, "to" is singular, "slova" is plural. Literally translated it would be "That are big words". But that's no proper English grammar, because you need a plural pronoun for your plural verb in English. In German, it is the same phenomenon as in Czech.
Yes. Agreed. Now those could be a dem. pronoun used alone or could act like an article if tied to a noun. "Those (n, pronoun, and stands alone as a noun of sorts) are pretty girls." Or, "Those (modifies and identifies like the article 'the') girls are pretty." Pretty simple.
Actually, velka' modifies slova, so it's saying there, "big words". So the right translation will contain the phrase "big words", but the meaning doesn't seem to be lost either way you wish to say it. So if translating this sentence, Those are big words is correct; but if you are trying to communicate that idea, you can say either way, but there are the subtle differences discussed on this page between those = pronoun and those = article or modifier. "Those" the pronoun can be a subject of a sentence, but "those" the modifier cannot be because it is not a noun or proNOUN.
My comment is a suggestion also. I'm starting to have to slow down to review the rules for endings, adjectives and nouns. I see I need to review or research because I see no lesson yet that explains plural adjectives, or adjectives that modify a plural word, like "velka' slova!" I see where o changes to a, but I did not locate where velke must agree with slova, though that seems intuitive enough. And I realized I need to look at "To" and ask, would I have said, Ta, for example. I scrolled up and down my notes up to this lesson and see no teaching on this.
(The Demonstrative Adj Ten:) Ten to ta, (Demonstrative Adjectives:) ti ty ty ta
This part seems more difficult to grasp than other parts up to here. I'm doing the English to Czech questions the hard way by reading the English, the figuring out myself how I would say that, and only then, looking to find that in one of the solutions. Because using the 3 answers like a cheat sheet means not making that effort to remember and to flow or try to flow as if one were on the streets live in action conversing in Czech.
Maybe if someone has a comment, or change that can be added to facilitate this, it could be helpful.
Of course, some areas just need a lot of review, but I really don't think some of this was addressed yet. But that's good practice because in real life, we'll see a lot of things we haven't addressed in class before.