[Grammar] That vs what vs how

[dz420]

1) English isn't that important that you think.2) English isn't that important what you think.3)English isn't that important how you think.Which one of the three sentences is correctly written? And why are the others wrong? I am so confused with "that vs what " and sometimes with "how"

 

[Rover_KE]

This is how your post should appear:

1) English isn't that important that you think.
2) English isn't that important what you think.
3)English isn't that important how you think.

Which one of the three sentences is correctly written, and why are the others wrong?

I am so confused with "that vs what " and sometimes with "how".