Nyob zoo Michelle! I'm so happy that you're interested in learning Hmong. It's my first language, but i still struggle from time to time. However, i tried my best at correcting your sentence.

You wrote: Nyob zoo! Kuv yuav txiv Hmoob Tus txiv neej;
Which means: Hello! I marry Hmong man/guy.

The word for 'boyfriend' is 'hluas nraug'.

Hmong: Nyob zoo! Kuv xav kawm lus Hmoob vim hais tias kuv thiab kuv tus hluas nraug xav sib yuav. Nws yog los tawm ib tsev neeg Hmoob uas coj kev caij qwb.
English: Hello! I want to learn Hmong because me and my boyfriend want to get married. He is from a traditional Hmong family.