The structures 不知道…多少 and 不知道…多么
The structure 不知道…多少
The structure 不知道…多少 
indicates that an action has been repeated many times.
For example, “I don't know how many times I've tried to bake this cake (I've tried to bake it many times)”.
indicates that an action has been repeated many times.
For example, “I don't know how many times I've tried to bake this cake (I've tried to bake it many times)”. Pay attention
In some cases, 不知道 can be shortened to 不知.
Scheme
不知(道)
verb/verb phrase
多少
measure word/noun
Pay attention
A verb phrase is a combination of a verb and an auxiliary word. The auxiliary word can be either an auxiliary verb or an object.
Examples
不知道给你打了多少次电话，你怎么不接呢？
I’ve called you so many times. Why didn't you answer?
bù zhīdao gěi nǐ dǎ le duōshao cì diànhuà, nǐ zěnme bù jiē ne
他在国外留学，不知道得花他父母多少钱
He's studying abroad. I can't imagine how much it costs his parents
tā zài guówài liúxué, bù zhīdao děi huā tā fùmǔ duōshao qián
这种方法我们已不知试了多少次
We have tried this method many times
zhè zhǒng fāngfǎ wǒmen yǐ bù zhī shì le duōshao cì
The structure 不知道…多么
The structure 不知道…多么 indicates the highest degree of something.
For example, "he hates me so much".
indicates the highest degree of something.
For example, "he hates me so much". Pay attention
In some cases, 多么 can be shortened to 多.
Scheme
不知(道)
verb/verb phrase
多(么)
verb/adjective
Examples
要是他知道了这个消息，不知得多高兴
He would be very happy if he knew the news
yàoshi tā zhīdao le zhè ge xiāoxi, bù zhī děi duō gāoxìng
她不知道他是多么爱她
She doesn't know how much he loves her
tā bù zhīdao tā shì duōme ài tā
你不知道你现在来是多么幸运
You can't imagine how lucky you are to be here now
nǐ bù zhīdao nǐ xiànzài lái shì duōme xìngyùn