Dear Jie Ran,

Wo ting 听 – I hear Wo bu ting
Wo dong 懂 – I understand Wo bu dong – I don’t understand
Here ting and dong both are verbs so
Wo tingbudong means litterally I hear but I don’t understand,
Wo butingdong could mean wo bu ting he wo bu tong (I don’t hear and I don’t understand, but I think it makes no scense)

听懂 is perhaps an abreveiation of opposite of 听得懂 which means I hear An I am able to understand. Her ite is clear that Bu should be between Ting and Dong.

in ChiFan 吃饭 Chi 饭 is a verb and fan is a noun. This a very special type in
Chinese a verb together with its object to form one word. Since Fan 饭(rice) ia
a common food in China ChiFan 吃饭 EatRice is considered to mean to eat, it is called a LiHeZi in Chinese. An other example are JianMian 见面 to meet (meet face). Therefore when negated you should say wo bu ChiFan I don’t eat rice, I don’t eat ( Chi Bu Fan could mean I don’t eat rice, but it makes no sence since a noun cannot be negated by Bu 不 I believe but with MeiYou 没有 or BuShi 不是 Wo mei you Fan, Zhe Bu Shi Fan, but never Bu Fan).
(also you cannot say “wǒ zuótiān jiànmiàn wǒdí gēgē 我昨天见面我的哥哥” because Jian already has an object and cannot get a another one you should say "wǒ zuótiān hé wǒdí gēgē jiànmiàn "

Hope this make it a little bit clear to you.

Roland Parijs