"How are you doing?" asks for detailed, direct responses about feelings. "How are you?" is a polite greeting requiring only positive responses. British English uses "Are you OK?" instead of "How are you?"
"To be" is the most common and complicated English verb. Forms include am, are, is, was, were, be, being, and been. Means to exist, occur, or have characteristics
Do and does are present simple forms of irregular verb do. Do is used with I, you, we, and they subjects. Does is used with he, she, it subjects. Negative forms are don't for do and doesn't for does
Can is used for both asking and giving permission. Could is more formal than can for asking permission. May is the most formal way to ask and give permission
"But" is commonly used to express contrast or exception. It functions as a coordinating conjunction connecting independent sentences. Can also be used as a preposition or adverb
Infinitive form: "catch" for all subjects. Preterite form: "caught" for all subjects