There are a number of differences in Czech and English between plural and countable nouns. We say watch, you say watches. You say hiccup, we say hiccups.
Another good example is with the word dress. Šaty is plural in Czech but singular in English – and while Czechs are often able to use the word ‘dress’ correctly, they often use it with a plural verb.
For example, a Czech student might say, “I love your dress. They are lovely.” To an English person, this sounds very confusing. How many dresses is this person talking about? One, two, every dress she owns?
So, stick to singular – “I love your dress. It is lovely” – when you are talking about one dress. And use plural when you are talking about multiple dresses – “She always wears such nice dresses. They are beautiful.”