Qigong marathon.

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- You "tell" someone something. (Example: I told my teacher I am happy.) You "say" something when you speak. (Example: I said that I was happy.)

- "Practice" is already a verb, so you don't need to say "I do this (v.)". You wouldn't say, "I do swimming every day."

- "Near" is distance. (Example: I live near the train station.) "Nearly" is time. (Example: It takes me nearly 5 minutes to get to the train station.)

- A "marathon" is where you must run 42 km. Marathon is also where you do something for a really long time. (Example: We are having a Lord of the Rings marathon. --> We will watch all three Lord of the Rings movies in one night.) I think that a more suitable word is "competition."

- If you "have to" do something, then it means that someone is forcing you to do it. (Example: The thief made me give him my money.) It has a bad meaning, but if you must do it because your teacher says so, then it is correct.

- "With using" is wrong. You can say "with her webinars" or "using her webinars," but not "with using her webinars."

- "Webinars from her" is not wrong, but "her webinars" sounds better.

- "I like to do" is very simple; "enjoy" makes it sound like your English is better. :D

- If you say "these," then the noun must be plural. (Example: This dog, these dogs.) Practice (n.) is usually used when you are practicing with a team, like basketball or volleyball. You don't really use it when you are practicing by yourself.

Hope that helps you!