你好，我是 Alex。

我在学习中文。我现在想找一个中文老师，中文应该是它的母语，还有我希望它有老师经历。*“它” :(

我有英文老师经历。我教过大人和青少年。These sentences are not wrong per say, but compounding them into one sentence would streamline things.

请问跟我联系。 

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Here's a preliminary revision.

大家好，我是Alex. 我想找一位中文老师，最好是有教学经验、责任心强的中文母语者。我自己曾经专业教英文，有成人和青少年的教学经验。如果您有兴趣，请和我联系。

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technical stuff

Unit/ counters: "一个" is not wrong when you are counting human beings.  "一位" is used in a formal-ish setting, implying his/her position is respected. For example, [他是一位很有名望的医生。 He is a very well-known and well-respected doctor.] Traditionally, Chinese people respect 医生，老师/教师，科学家，工程师。 （an example when 一位 is not used: 一位流浪汉 a homeless person)

talking about one's preferences: In a formal hiring setting, it's common to see a bullet list like 岗位要求/招聘条件， and the preferences would be written in the boilerplate form like "有xxxx经验者优先"、“有xxx以上经验者为佳”。When you are not doing a formal/official hiring, it is important to be direct, but not coming off arrogant. "Chinese should be its mother-tongue, and I hope it better has some teaching experience" can sometimes sound a bit 不庄重。

Overall your paragraph is well-written, I'm sure you can find a great teacher soon! Good luck.

Hi Alex 

I would like to be your language exchange partner.