i have many things want to do and see.

不对的,可以直接说I have many things to do and see.这里不定式充当谓语成分,我有许多要做和要看的事.
如果像楼主那么说的话,就出现多余的谓语啦丫……
不懂可以追问呦……
再问： i have many things that i want to do and see.这句对吗？
再答： 嗯嗯，这样也是对滴呢，这样就组成了一个定语从句啦！很不错呦……