Thank you. I do not need an English teacher. I only had this question.

The preposition "by" is used in many different ways.One common use is in place phrases. In showing places, the meaning of "by" is the same as "beside" or "at the side of". For example: He was sitting by the door./ He parked his car by mine. Another way that we use "by" is when it is used with a verb showing motion, it usually shows movement past a place. Examples: Who was that man who just ran by us? / we walked by the store this morning. with a pronoun it also means having sth in an easy to reach place or on you. for example: I usually have a pen by me. / you should have a dictionary by you to learn words. and also when "by" is used to express time it means"not later than". Examples: I'll be there by evening. / He must arrive by 10. and about "for" I should say: It is used to indicate the use of something. for example: My mother baked a cake for my birthday. / I should study hard for the exam. It is also used to mean "because of". Examples: I'm really sorry for his death. / for many reasons, I left her house. Another use of "for" is to express time or duration. For example: I've been there for many years. / He was waiting you for two hours.