боғи ботаникӣ: botanic garden
In the big cities of Australia there are botanic gardens.
Дар боғи ботаникии шаҳри Душанбе садҳо дарахту буттаҳо аз тамоми гӯшаҳои ҷаҳон ҷамъ оварда шудаанд.
In the botanic garden of the city of Dushanbe hundreds of trees and bushes from every corner of the world have been gathered.
You can’t have the letter ӣ in the middle of a word. In the second sentence, there is added information after “боғи ботаникӣ”, that is, which botanic garden, the one in the city of Dushanbe. To connect that an extra и has to be added to the end of ботаникӣ, and the letter ӣ must also be changed to и.
ботаник: botanist (also гиёҳшинос)
ботаника: botany (also гиёҳшиносӣ)
The botanic garden in Dushanbe is in this list of top 10 places to visit in Dushanbe. Read about it and the other places here: 10 ҷойи ҷолиби Душанбе.
For more information on the Dushanbe botanic garden and its history, see this article on Wikipedia: Боғи Ирам.