一個自己我介紹

我而家喺呢個充滿機會嘅城市搵緊工。

我嘅工作經驗包括Content Marketing，Social Media Marketing，SEO（搜尋引擎優化）, Pay-per-Click advertising, 同埋 平面設計。

我對Google，Microsoft BING 同埋 中國社交媒體 例如 微信 同埋 新浪微博 都有所了解。

我喺創業公司度做過*嘢，亦都喺大型傳統企業做過*嘢。(*Your original sentence means you are currently working at these 2 enterprises. But if you meant past experience - add "過")

我識講多種語言，不斷喺多元文化城市充實我嘅跨文化交流技巧。

我(好*)勤力，不停學習新事物，上堂improve(提升)自己。("好" is optional, but the whole phrase sounds more natural to me)("improve" is fine, as we (Hongkongers) tend to mix in a lot of English in our daily speech anyway, or replace it with "提升". Alternatively, simply say "上堂進修".)

Well done! Very natural speech. And good luck!