It has two functions: 1. 'Did' is the past tense form of 'do'. I do my homework every day. = present I did my homework yesterday. = past 2. 'Did' is used an an auxiliary verb for questions in the past tense. You use 'did' with the infinitive (base form) of the main verb. Did you go to school yesterday? Did you see that film last week? The negative form of the past tense uses 'didn't' in the same way. I didn't go to school yesterday. I didn't see that film last week. Only affirmative sentences use the actual past form. I went to school yesterday. I saw that film last week.

"Did" is the past tense of "do." There are many ways to use it. Examples: "Yesterday I did what you asked." "Yesterday I did write a paper." (this is called "do-support," used for emphasis.) "Did you write a paper?"

It's correct I talk ( I did a running of bicycle ) ? and You did explained lesson of the University ?

Carlos rode his bicycle. Maria did also. Did you speak with Juan today? Paco gave a speech in front of 200 people. I wonder if Gabriel did also?