Questions & Answers about Porque es muy importante.
The lesson taught por qué for "why". Why is this spelled porque?
Where is the word for "it" in this sentence?
Spanish usually drops the subject pronoun when talking about "it". You just leave it out. The verb es translates to "it is" in this context, and the listener will already know what you are referring to.
Could I say mucho importante instead of muy importante?
Does the ending of importante change if the thing that is important is feminine?
No, adjectives that end in the letter -e stay exactly the same for both masculine and feminine words. They only change to add an -s if the things you are describing are plural (importantes).