Я хочу изучать:
- "время" будет "времени" с родительном падежом
- много makes things genitive
I'm not sure if "требует" is the right verb for to "to take (time)"; please suggest a better one if it doesn't sound right!
Изучать русский язык требует много времени.
Требует много времени is perfectly fine!When you wanna say that smth takes much time ,it's just the right phrase to use.But in the first part it's better to say Изучение языка.It's like gerund in English.Gerund is translated into Russian with the ending -ние.Learning Russian -Изучение русского.or reading -чтение and so on.