英文i got an apple from or by

In" I will be back",the "be" =auxiliary verb;In will be, the word "will"is modal verb used to express the simple future tense:-A meeting will be held...
What time will I arrive?
When will I arrive?
It is used like "must" to show what you think is likely to be true.
That will be me coming to the office.
Hence "I will be back." has the determination to do something that you have decided to do, even if you've not enough time or as a free will saying or conversation.
Will you be coming back ?
I will be back soon.
Be back.

The Adverb:- adverb is a word or group of words that describes or adds to the meaning of a verb, an adjective, another adverb, or a whole sentnece.
eg:-It's very hot-----very is adverb
I am very happy----very is an adverb
She ran slowly-----slowly is adverb
Happily, we want you to come.-----Happily is adverb
Fortunately, we won the game.-----Fortunately is adverb

The adjective:-adjective is a word that describes a noun or pronoun;that describes a person or thing,or gives extra information about them.Adjectives usually come before nouns or after link verbs, such as "purple" in the sentence,"She wore a purple hat."
"happy" in the sentence.,"I am happy".
"good "in the sentence,"I am a good boy".
"big" in the sentence,"He wears a big hat !"
"dead" in the sentence,"Her husband is dead !", meaning dead husband.
"financial" in the sentence,"HK is a financial city,a financial success ! "
"financial" in the sentence,"The City U got financial assistance".

I got an apple from:-
eg:-from prep. means given by someone
eg:-I had a mobil phone from Jobs; from the owner; from Steve and Jobs.
"by" prep, is used with a passive,or verb to show the person that does something:-eg:-The mobil phone was designed by a famous architect.eg:He is alarmed by the tone in alarm-clock+phone.
In using or doing a particular thing:-eg:-You can reserve the mobil-phone by phone.Send it by airmail.He earns his living by selling mobil-phones.

其實用from或者by係視乎你句句子想講乜。examples:
I got an apple from Tom - 我從Tom處得到一個蘋果。
I got an apple by helping John to solve a math quiz. - 我得到一個蘋果,是我幫John解決一條數學題而得的。