Honestly, I think they should change this to make sense. It's one thing to test us on the endings, but considering that things are said differently in Czech than in English, it doesn't help me to learn things that no one would ever say. For example, is it correct to say "one egg" in this context? I don't know enough about the language to not make a fool of myself.
I looked up "egg" and i looked up "vajíčko". My dictionary says that "egg" is "vejce" and "vajíčko" is.... something anatomic - and also an easter egg when combined with "velikonoční". So i gather that (if anything) "vajíčko" is a small egg and definitely no ostrich egg.....
While "vajíčko" is a diminutive of "vejce", the meaning is pretty much the same in contemporary spoken Czech. Some diminutives lost their 'diminutive meaning' and mean basically the same as 'normal' words. "Vajíčko" is one of those. "Kniha/Knížka" too, for example.
Vajíčko is any egg, really. Even an ostrich one https://www.google.com/search?q=%22vaj%C3%AD%C4%8Dko+p%C5%A1trosa%22
Or an animal (or human) oocyte or ovum.
In general, any dictionary without examples and explanations is insufficient. If it only lists possible translations you can never be sure when they are applicable.
No, I do not know any such dictionary in Czech or German except some completely obselete ones from the 19th century.