A job I would like to do to have. 

A job I would like to do to have would be a Japanese teacher teaching Japanese in an English speaking country. I've been studying English for 3 years and I sometimes talk to foreigners who want to learn Japanese on via Skype. Seeing them improve their Japanese skills makes me really happy, and I realized how much I like teaching my mother language to foreigners. They often ask the difference in meaning between similar words, which I've never thought about before. Therefore, although I'm a native Japanese speaker, I need to study Japanese to gain deeper knowledge so that I can answer their questions.
To be able to a Japanese teacher, you definitely need to understand the Japanese language deeply and correctly. Also, you have to explain well to make your students understand. I'm not good at teaching, but it would be really enjoyable for me to know different cultures through teaching. Furthermore, their attitudes, behavior and values could inspire me.

Infact, now I think about it. This is the casual way of saying it. The formal would be '' いわないといけません''

The meaning of this is weird. It means something like '' I have to tell ''.

Could you please give me some context?