Here are the appropriate forms of the verbs for each blank in your text:
Esperanto is a constructed language. It was created (25) by physician and linguist L. L. Zamenhof. His idea was (26) to create a language that would be easy to learn and would help people from different countries and of different nationalities understand each other. L. L. Zamenhof was born and spent (27) his childhood in Bialystock, a city in modern-day Poland. In those days, the population of the city consisted (28) of Germans, Jews, Russians, and Poles. Cultural and language differences separated the people into four groups and they did not want (29) to communicate with each other. Zamenhof believed that a common language would improve the situation not only in his community but in the world too. Nowadays Esperanto is spoken (30) in Europe, East Asia, and South America. You can learn it on the Internet, as lots of online Esperanto courses are available.