Learn Turkish: Finali izleyecek misin? Çünkü çok önemli. - Will you watch the final? Because it is very important.

Let's break it down: izle (watch) + -y- (buffer letter) + -ecek (future suffix). Then, we write the question particle mi as a separate word and attach the "you" ending -sin to it. Notice how the personal ending attaches to the question particle, not the main verb!

Why does final have an -i at the end?

That is the specific direct object (accusative) case. Because you are asking about watching a specific, known event ("the final" rather than just "a final"), final takes the -i suffix to become finali.

Why do we use misin instead of mısın for the question part?

This is because of vowel harmony. The question particle matches the last vowel of the word before it. The future suffix -ecek ends with the vowel e, so the question particle must be mi, and the personal ending follows suit to become -sin.

How is the word önemli built?

It comes from the noun önem, which means "importance". The suffix -li means "with" or "having". So, adding them together makes önemli, which literally means "having importance" (important).