So I began learning Spanish last weekend. It was mostly Duolingo. ~700 words are in the vocabulary. Not sure how many of them I really know :)
In fact a lot of words weren't really new.
Some words are exactly the same as in other languages, for example "the animal" is "el animal" or "библиотека" is "la biblioteca".
Some words are almost the same as "der Pistole" and "la pistola" or "the calender" and "el calendario".
Spanish, as many other languages, has many loan words, so this makes things easier.
Also in some cases things are simpler due to the endings - the world ending can change the gender the word, so that you need to learn only one word and not two:
la gata/el gato - the female/male cat
la hermana/el hermano - the sister/brother
But, of course, not everything is easy. For example, Spanish has more pronounce: they distinguish between "him" (lo) and "to him" (le). Also verbs have much more endings. In some cases word order is different.
During this week I learned several hundreds of most common words and the grammar for basic conversations. Next week I'm going to concentrate more on verb forms.
Anyway, learning a new language is a really interesting experience :)