"还有" (háiyǒu) is used to express "In addition..." in a conversation. It is introducing new information to the topic the speaker(s) is/are talking about. While it's not the most challenging grammar structure, an important thing to keep in mind is that 还有 starts a completely new sentence or clause.

Structure
It's as simple as using 还有 before the new clause or sentence. 还有 can also be used with a comma, similar to how we can say "in addition, . . ." in English.

Examples

Pǔ tōnɡ huà hěn nán. Hái yǒu , zhuān jiā jué dé rì yǔ 、 ɡuǎnɡ dōnɡ huà 、 hán yǔ, zhè sān mén yǔ yán yě hěn nán.
普通话 很难。还有 ，专家 觉得 日语、广东话、韩语，这 三 门 语言 也 很难。
Chinese is very hard. Furthermore, experts think that Japanese, Cantonese, and Korean are also hard.