"Why I refused." is a sentence while "How to make both ends meet." is a fragment. I can turn it into I am learning how to make both ends meet. Is this correct?

Why I refused = not a complete sentence. You can make it complete if you turn it into a question (Why did I refuse?), but as it is, it's still a fragment.

How to make both ends meet = a fragment, yes. And yes, your way to make it a complete sentence is fine.

THANK YOU SOO MUCHHHH BRUUH

You're very welcome!

Almost! "I am learning how to make both ends meet" is indeed a complete sentence and can be considered as a revised and complete version of the original fragment "How to make both ends meet." However, I must clarify that the original fragment "How to make both ends meet" is not a sentence on its own because it lacks a subject (a noun or pronoun that performs the action) and a predicate (a verb or verb phrase that shows the action or state of being). By adding the subject "I am learning" to the fragment, you have created a sentence that is grammatically correct and conveys a complete thought. Hence, your revision is indeed correct!